Join Date: Sep 2006
Location: Aurora, CO
Bikes: 2005 Performer Toscana, Kona Hoo-Ha, RANS V3 steel, RANS City
USS (under) fans say it feels more relaxed and natural. It definitely offers a better view of the road. It also might be easier to mount/dismount the bike with USS. As mentioned, it is less aerodynamic (not really an issue for touring). I've heard that it is twitchier and harder to learn in the beginning. Also, harder to mount mirrors, computer, etc. on the bars. Could also be a small weight penalty. In a crash, you might fly off the seat (could be bad, or good if you land on your feet). Its harder to walk while pushing the bike along. Finally, recumbents with USS are less common, but there are some good bikes out there.
OSS is more intuitive. The bike will be faster because of the narrower profile. Its pretty widely available. By far most lowracers are OSS only. It offers a greater range of arm positions (hamster, superman). Its easy to find different replacement handlebars and stems. Easy to mount accesories. Its easier to push the bike, up a hill, let's say. One negative is that it may take longer to dial in if you have short arms, but its easy to make adjustments. Also, if your bike has a lot of tiller, it may feel slightly weird pushing your hands to the side.