Honestly, from a bike fit perspective, SPD pedals offer the least in adjustability. That's really the only reason to avoid them. Double sided doesn't really come into play b/c 3-hole systems (Keo, Shimano SL, etc.) counterbalance their pedal to stay upright and Speedplay are also double sided. So, if you're going to be spending a good amount of time pedaling, I'd suggest a more adjustable pedal system and go to a reputable fitter. For my $, I'd go with Speedplay Zero's and find a fitter through bikefit.com