These bikes are in a very similar performance class. However, I looked at Sporsters first when I came back to two wheels last year, and like you, I discovered they didn't fit me well. Probably because I rode an HD TourGlide back in the '80s and early '90s, the Sporsters feel like toys. The America is different, more like the big V-twin cruisers, but nimble and better handling. Most of my riding is commuting to work at speeds around 50 - 80 MPH, and the America is perfect for that. I'm sure lots of folks here can attest to its usefulness on long tours also, I just don't get to do that anymore. I think the bottom line to all this is that the Sportster frame is too small. If it doesn't fit you as-is from the factory, it's time to move on.
