Between the S40, S50 and M50 I wanted to know how they compare in passenger ride comfort and how well the bike handles the weight in terms of power loss. Looking for the cheapest option for a primarily commuter bike that will also be capable of putting my wife on the back to take occasional weekend trips in the 200 mile range. So any details you guys could give me on how these 3 bikes stack up in that regard I would appreciate. Thanks.