In mountain biking, there is currently a great debate on what is the better wheel size. There is a general consensus that 26 is dead. but beyond that there is disagreement. There was a time when the debate was clear cut. 29 was for XC, 650 was for trail and enduro riding, and 26 was for DH. Then DH racers switched exclusively to 650. Enduro riders started to ride 29 or 650. Smaller xc riders started to use 650. Then things became even more jumbled when Santa Cruz gave their race team a prototype 29 DH bike. Being an XC racer, my bias is towards 29. It is faster rolling and has a better rollover characteristic which makes a huge difference on short-travel XC bikes. It is more efficient on climbs as well. 650 (or 27.5) has a very nimble and quick feel. The smaller wheel size allows them to change directions quicker than 29, giving them a hypothetical advantage in downhill. But, because they are smaller, they do not roll over obstacles as well as 29. They get hung up on roots and ruts easier than a 29-inch wheel. My opinion is that 29 is fast, 650B is fun. 29 is the wheel size for the racer and 27.5 is for the partier.