When I was test riding, the only real difference I noticed was that big cracks and potholes were not only more jarring on the smaller wheel, but sometimes would affect my steering if I was not very careful. Kind of like going over railroad tracks with a regular bike, as an example. As long as you pay attention to what you are doing (which means good lights if you ride at night), it is fine. I ended up with 20" wheels because the roads I use are just the crappiest and will probably never get fixed.