I have a Co-Motion Speedster tandem that came with 700c wheels. I recently changed over to 650b. With a slightly smaller wheel diameter, I was able to use wider tires so the pressure is lower. The ride is more comfortable, even on asphalt. Lower pressure will more than compensate for the slightly smaller wheel diameter. The difference in radius is something like 1/2"-3/4", so hardly enough to affect ease of rolling over bumps. Fenders fit with more clearance. The feel of steering is a little different with the 60b - sort of like having power steering on a car. I expect this effect depends on the bike's specific bike geometry, weight distribution, etc. It's not bad, just different. The selection of 650b tires is more limited than 700c, but it is adequate. Same thing with wheels, both new and used. Interest in 650b seems to be growing, so I expect tire selection will improve. 650b has been around for a long time, so I don't expect it to go away in the near future. I expect 650b tires will be generally available in the US and Europe, but don't know about Mexico.