Want to ride all night on a regular basis, or commute all year round? A dynamo means you never have to worry about battery levels, and fitting an E3 Pro will mean you don't have to worry about not having enough light either. It's a very well built unit with a great beam pattern that's more or less perfect for road cycling.
There’s a constant struggle going on to develop a bike light with enough illumination power to rival Blackpool, a run time long enough for the longest of nocturnal enduros, and all in a package sufficiently small and light that it won’t weigh you down. Usually, there’s a trade-off of some sort, but increasingly, as improving LED technology couples together with new lighter, higher capacity batteries, it’s a tough call for the cyclist looking to choose a new light. There are some really great ones out there now.
If you want a permanent lighting solution for your town bike then the magnet-driven Reelights are an attractive option. They're much easier to fit than a hub dynamo system – though attaching them isn't wihout its problems – and offer reliable, free lighting with negligible resistance. The SL520 system, which stores energy for your stops, is a better town option though.