They are about equal in ride quality; the UO-8 has an original pump (which can be hard to find) and is older (somewhere close to 74), the UE-8 has the fenders which are very nice. To me the biggest factor is size: the UO-8 looks to be a 23"+ size, while the UE-8 looks to be a 21" or smaller. Buy the one that fits!
Mark