650. It is a lot better on the blacktop where you will spend most of your time. It has a lower seat height, the 400 is a pretty tall bike. As a commuter the 650 is superior, and will be WAY better at speed on the highway. The 400 is better offroad, but you probably wont be running real knobbys anyway and therefore not capable of pushing hard offroad. I Get the 650, put it on some blacktop friendly dual sport tires, enjoy a decent commuter and live with the somewhat limited offroad capability. Offroading is great fun, slow or fast.