The functional differences are that the america has more top end power while the SM has more low end torque. The speedmaster has dual front discs, a tach, and alloy wheels. the rest is all cosmetic and totally subejective and therefore 100% up to you. I wanted the discs tach and alloys so i went with the SM. I also found the black engine makes for a bike that looks cleaner easier and longer and takes very little work to make it stay showroon clean and new. The america is IMO a bike you buy if wire wheels and a non black engine is important to you cosmetically.
