Welcome
I'm a big girl, 6' and FAT...lol...and the M is fine for my size. It zips around the hills and highways with no power issues (other than that elusive 6th gear...you'll find yourself trying to shift up from 5th, because it'll seem like the bike needs to). I love the bike, it's my first bike, and after 3 years, I'm still happy with it. I'd love the M109 at some point, but I'm very content with this bike. Hope that helps