Dedicated GPS vs iPhone vs Smartwatch?

I use my phone. Battery life is fine so long as you don't have the screen on all the time. You can also take a powerbank in case you run out of juice. OSM provides excellent downloaded maps with which to use Strava-plotted routes. Glove mode in Android works OK at this time of year.

The most practical device is a dedicated bike computer. They are water proof, easy to mount, has a screen that is easy to read in sunlight and the battery lasts all day. Not so with a smartphone.

I had a Suunto watch but that was really unfit for the purpose. It is very unpractical/dangerous having to turn your wrist and then turn your head to see the watch so you're not looking at the road which of course can lead to an accident. Finally it's extremly difficult to read the data from such a small screen at a quick glance. I know you can mount most watches to the handlebar but the screen is simply too small.

If you want to save money and get something that works everytime, try Lezyne.

Phones are a great option for a lot of bike navigation and activity tracking and are by far the most flexible devices. However, the price of that flexibility is compromise; the apps target general-purpose operating systems on general-purpose phone hardware that is concurrently running many other apps.  Compared to a dedicated device the experience will tend to be less reliable, have more user interface compromises (buttons are handy, unlocking is a pain with gloves or when wet), be less robust/waterproof and with far worse battery life (especially when cold and if your device is designed and tested in California).

I regularly use both an iPhone and various Garmin GPS devices, individually and together.  Short, around town navigation and tracking, is done on the phone with Strava/Ridewithgps/Google maps.  For multi-hour road rides, I use a Garmin 820 (which works just fine for me).  Multi-hour off-road riding mostly uses the Garmin as well, but with the phone ready to hand so that I can quickly get at quality OS mapping on a large display.

All the different options work well enough in different situations. In my experience, whether or not the performance difference between the phone and the dedicated unit matters has depended on the type of riding and how much I've been prepared to put up with versus the cost to fix it.  For me,  at the moment the convenience and the additional safety factor provided by a couple of independent navigation options for when I'm in the middle of nowhere justify the Garmin.

For you, if you're not sure I'd think about sticking with the most "economical" option of the phone for now and investing in a good mount system (Quadlock are excellent).  If worried about battery life, try using the phone in its low power mode. If still worried about battery life then the combination of a fuel bag,  a 10,000+ mAh powerbank and charging cable will see out most days of riding with the display on a lot. If after trying that the other issues are annoying, then you'll be in a better position to make sure you buy yourself the right dedicated GPS unit option. Otherwise it's money saved, or rather extra money to spend on the bike

For a couple of years I used my Galaxy S8+ as my cycle computer with a Quadlock case and outfront mount (previously used the same set up on IPhone). It was excellent - especially for the mapping. However, it was a killer on battery life. Last year I switched to an Edge 25. Completely different experience - small screen, basic navigation- but I love it! I plan my routes in advance and can get on with the navigation fine. I got a cheap 2nd hand bundle with all the sensors.

Another long time 800 user here.  I’ve looked at the newer ones, and decided that the 800 is fine, and seems to work for me, so I’d not worry much about the tech cycle as long as the piece of kit works.

I use my iPhone to track as well unless I’m going for a long ride (4hrs plus), when I save the battery and just use the Garmin

FWIW, MotionX do a GPS app that is worth the purchase of an iPhone, just to get that app.  It will record a track and spit out a GPX file at the end of it.  You can also use iTunes to get your GPX file onto the phone, and so plan a route on Strava, RideWithGPS etc. and then follow it.  You can also set it to send 'live updates' of your position at periodic intervals to your loved ones, or even to Facebook if you're into that.  

As you quite rightly point out, however, battery life is the big issue.  You can either buy a battery pack and carry that with you (this one rides in my commuting backpack as a permanent fixture), or you can get a hub dynamo. 

I use a Garmin Edge 800 on my commute, for the simple reason that my iPhone XSMax isn't insured and that's a lorra lolly to shell out, should I fall off the bike during the ride.  The Garmin is utterly shit for navigation, but brilliant if all you want to do is log the ride.

I have a heart rate monitor that used to go around the chest, but got an Apple Watch a couple of months ago, and I use that to keep track of my rides, as well as my heart rate etc.  It's been said that it's not as accurate as a chest device, but I've not noticed any massive discrepancies since I started to use it. 

I went from the Garmin 520 to the Fenix 3 and now have the Fenix 5 (bit smaller and HR) but would defo look around eBay for Fenix 3 as they are great and can use it for running, swimming, steps etc

PS the saphire has a non scratch screen and is more in demand but I mountain bike with mine and never had a scratch 

https://www.ebay.co.uk/itm/garmin-fenix-3-hr-sapphire/173759190102?hash=...

Having trashed an iphone when it fell off the bike my solution is as follows:

3 year old Garmin Edge 1000 on the handlebars (115g) + 5g Mount - Old and slightly flawed but it works fine and sync's wirelessly to upload rides to my strava and shows favourite segments in real time. Plus I want maps (all western europe is included) and the ability to put in detinations on the fly if I need to.

Elari Nanophone C (95mm x 35mm ) 30g in a small  plastic bag in my back zipped jersey pocket with house key, credit card and £10 note.

In my experience phones can be a problem with regards reduced battery life especially when running strava and with the display permanently on.

The one and only time I used my phone on the bike was in the Autumn when I was in the wilds of Cornwall, on roads I had never ridden before and 2/3 of the way through the ride my breadcrumb trail became iffy to follow (Garmin Edge 500 user here). I fired up Google Maps to get me back to the hotel in one piece noting that my (fairly cheap) phone seemed pretty vulnerable and quite distracting with its big colourful screen. 

When I aam at home I have a tiny PAYG Alcatel dumb phone to take out on rides and exclusively use the 500. 

In tech terms it is very very old, and I would like to upgrade to the 520 Plus when I have the cash, but only because the mapping and navigation would be a big step up from what I have. Everything else the 500 does really really well, and I will happily keep riding with it until I can afford to upgrade. 

And this from a tech nerd who loves to always have the latest iteration of gadgets whenever he can. 

It really comes down to what you need or want from the unit. Please don't take this as an insult, as I've been there myself, but it sounds like you just want some cool tech to stick on the bike. Bike GPS units aren't cool or interesting, they're always fairly dull and conservative devices compared to the leading edge of tech. They're very niche products; but, if you have a need or desire today for the functionality they do provide, agonising over that a future device might provide is largely irrelevant. Take a look at dedicated hiking GPS units, they’re a million miles behind the current crop of smart phones or watches. That gap isn’t going to close any time soon, if ever. Try using a phone for 10+ hours in the rain, then drop it onto concrete, ditto with a smart watch.

I've been using my phone for 6000 miles with no problems. Initially in my pocket, then  as I started to actively train more and push harder on improving my times on segments I started mounting it out front where I can see it (live segments on strava etc).

Only became a problem a month ago when the battery was deteriorating such that it could just about manage 4 hours with strava and komoot (for navigation) running. I've since upgraded the phone and am using it the same way.

I'd like a dedicated unit but right now I'm not impressed by whats available and too many stories of garmin issues. Wahoo looks the best bet but I'm in no hurry.

No one uses all the “features” on newer devices. My old edge 800 was faultless, I’m still not sure why I “upgraded” to an 820. I spent half a day figuring out how to turn off all the pointless rubbish off. Live segments? Stop beeping and turning the map on for goodness sake. Off. Text messages and email on screen? No thanks, I’ll check when I’m finished. Touchscreen is a source of endless frustration at this time of year. It does mapping and routes well, but so did my 800, which did all I needed it to do and all I want the 820 to do. I gave it do a friend then my 820 broke. At least the warranty claim was painless

If you're really worried about things being outdated then cycling is going to cost you a bucket load. Your bike is probably already out of date!

I started off with using a phone app which was fine for a while - start your ride, pop your phone in your pocket and you're good to go. However, that doesn't let you see time/speed etc whilst you're riding.

I got a Wahoo Elemnt Bolt last year and it's superb. Works a treat with connecting to other sensors (which are also Wahoo as it happens) and it's got more battery life than I'll ever need (12 hours?).

Stop worrying about it getting outdated!

Buy what you want now at the best price you can. I've been using an Edge 1000 for 4 years and it's awesome. Yeah outdated and a few quirks but no regrets.

Also use fenix 5 for 2 years and love it.

I was very excited about live strava segments when they came out, and disappointed that my Edge 800 couldn't do them.  Then I got an 810, which as far as I knew couldn't either, but it was cheap and my 800 had broken.

I found out a couple of weeks ago the 810 actually can do strava segments but since then I haven't even tried it yet.

My point... what seems very exciting in the latest model press release probably isnt.

You will be fine with a 520.  Or even a 510 for that matter...

Speaking as a tech-nerd, who's got/tried all options you mention, my advice would be to go straight to a version of the Garmin Edge 520 (either the older one or the Plus would be fine, the latter being better for navigation).

I was in a similar position to you last year, started off using my iPhone, then went for the Edge 25, then got a heart-rate monitor, then a speed/cadence sensor, then the Edge 520 (because the Edge 25 quickly showed it's limitations)... I stayed with this set up until last month when I upgraded again to the Edge 1030 (because I wanted the best navigation).

Along the way I picked up a Forerunner 235XT watch which I now use for other sports, as a daily watch (which it's great for) and the odd cycling commute, but it would in no way compete with the Edge units... you just get so much more back from a dedicated GPS head unit, it improves cycling and makes you do it more.

Also, for Strava, it's way cleaner... auto-pausing for one, and general accuracy, it gives you way better feedback in every area.

So, if I could go back and speak to myself, or you, I'd say get an Edge 520 bundle with the HRM and speed/cadence sensors... you can thank me later.

I've got an Edge 25 (passed on to my son) and an Edge 130.

Edge 25 is still a superb device for doing the basics well - the only reason I upgraded was because I use a power meter and wanted navigation and better integration with other apps

The screen on the 130 is excellent and very configurable - a noticeable improvement over the Edge 25. And I've had zero issues with either unit in terms of lost rides etc.

Both will do the job - personally I'd go for a used Edge 130 (always loads on eBay) rather than a 25, simply because Garmin will/should support it for several years.

Prior to the Garmins I had a few Wahoo devices - starting with the bike case which let me stick an iPhone on my bars. They were good, but somewhat geeky, and I started to get issues.

I wouldn't use my phone on my bars unless it was cheap/disposable.