Both the 650 and the 400 are very nice, but different, bikes. When I was in the market for a maxiscooter, I test rode both models. For LD touring, the 650 is the best choice in maxiscooters and compares favorably to big touring motorcycles. It has lots of power, great handling and brakes, very comfortable and stable. Felt very much like my buddy's BMW RT1150. I found the stock seat mildly uncomfortable and the stock windscreen was not good, so I would need to change out both of those items, which is fairly standard procedure with most bikes. For around town, the 650 is just a bit too big and heavy for me, especially since I had my foot surgery. The 400 had more power than I expected, it went from zero to 60 mph quickly. I liked its stock seat but I did not like its windscreen nor the less than pleasant one cylinder drone at speed. It would be a very useful, economical and practical bike for suburban commuting and errand running - huge trunk and enough power and presence to handle aggressive cagers.
BTW, I ended up getting a Yamaha Tmax. Not quite as suitable for LD touring as the 650, but a much, much sportier bike. The 500 twin is more powerful and smoother than the 400. On good pavement, the Tmax even outcorners my old GSXR 1000. In many ways, I feel the Tmax is the best handling motorcycle I've owned. It also has a perfect riding position for me. Both the stock seat and windscreen fit me perfectly. The Tmax fits in between the 400 and 650 in many ways and I have enjoyed owning it for the last year.
"Reason takes a holiday as Dr. Horrible spends money he doesn't have, on a motorcycle he doesn't need, in a misguided attempt to recapture his youth which, upon reflection, wasn't all that great in the first place."
"Ride to the bar in your pirate outfit, guzzle some beer, play "Free Bird' on the juke box and then go home. Badass."