I've got 16" wheels on my giatex. The advantage I've found for the smaller wheels are that it seems a bit easier to get up steep hills. Maybe that's just my imagination, though. I've also found that acceleration is faster (which is bad on a bike where most of the weight is in the back. I've almost fallen over backwards a few times). I think if my bike had better gearing and some form of suspension, the wheels would be fine.