2010 bianchi 928 c2c and 2002Colnago C40

Like two others have already said, buy the bike that fits you! And if neither bike fits, buy something else. That Colnago looks like a very large frame, by the way -- be careful to check the geometry of the Colnago frames, because they slope things differently which means their sizes don't match up with other manufacturers' raw C-C numbers.

As for which is better; they're both great bikes. The Bianchi is probably the more sensible choice, being newer, but I'd personally go for the Colnago -- they're just beautiful. The C40 was a pro frame, and it'd be an amazing machine to ride fast, but that's a two-edged sword -- it will probably make for harder work than a modern 'endurance' oriented frame on long rides. It'd be awesome though.

Edit -- ah, look at that, should have refreshed the page before I wrote a reply -- the Merckx will be an equally fantastic bike, good choice

Firstly, size, secondly, size.

Colnago is unlikely to lose any value, the Bianchi might lose a bit more

First of all, those two bikes are not the same size, so I think it's unlikely that they will both fit you equally well. That is more important than any other aspect of your decision, so pick the one that fits.

Second, there have been many improvements in carbon frame design and manufacturing between 2002 and 2010. Personally, I would favor the Bianchi for that reason.

Third, absent any detailed information about mileage or how much rough duty the bikes have experienced, I would guess the Bianchi has more life left in it.

I would pick the Bianchi, if it fits properly, or neither.

Both are newer and better spec'd than my current road bike. And I've never ridden either, so take this with a pinch of salt...

I think that the Bianchi may be a more comfortable ride, as it's their C2C range, while the C40 was part of the more aggressive Colnago racing (as opposed to endurance) lineage.

Personally, I'd lean toward the Bianchi, because I'm in the process of speccing one myself. The Colnago would be a bit much for me. But you might have different tastes and riding style. A test ride of both bikes would be the best way of finding out!

The Bianchi is reviewed here (sorry it's not road.cc, their review was for the B4P version). There's bound to be some of the C40 in the interwebz.