29"/700c
Pros:
- Wheels have more rotational momentum, and in theory should retain their speed better.
- Look better on bikes for tall people
- Lower angle on the outer circumference of the wheel tangential to the ground, allows you to roll over larger obstacles easier
- In my experience they tend to smooth out the road more
- I've observed far less flats with 700c tires. I theorize that there's a larger contact area and therefore my weight is distributed over more area, resulting in less pounds per square inch hitting the ground, which I think makes it so that road debris doesn't penetrate the rubber as easily. I could be full of crap though, and it's possible I just finally found a really good tire, and all the 26" tires I tried were bad. Who the heck knows.
- They have been touted as being more stable than 26". I do feel like they are, but my experience consists of comparing a mountain bike (not built for stability) with a touring bike (built for stability), so it's possible it's the bike that's making it more stable, not the wheels.
Cons:
- Wheels have more rotational momentum, so they are harder to accelerate and decelerate.
- In theory the longer spoke length results in a weaker wheel and for uber-clydes such as myself we may need to use more spokes. I have not witnessed this in actuality, however. After 8 months of heavy usage on 36 spoke 700c wheels, they are still as true as the day they were built.
- If you use wider tires, it may be hard to find a tube in dire situations. IE: if you don't have a spare, you'll be unlikely to borrow a 700c wide tube from a helpful passerby, because 90% of road bikers use really narrow tires. Big problem? Shrug. Hasn't been one for me, but I'm just trying to be thorough.
I love 700c/29er wheels. I'm sold on them, and don't think I could go back to 26". I might be willing to give 650b tires a try (they're about halfway between 26 and 29er tires) because with 700Cx40mm tires on my bike, the top tube hits my crotch, but it's not a huge problem and I can live with it just fine. Of course possibly a better solution would be to get a frame with a sloping top tube, but I don't really like the way those look.