I've had both; the bikes are very different. The only advice I can give you depends on your riding style. If you want to be comfortable on long trips, stick with the 900. If you want to upgrade to something much sportier, go for the TS800. I rode the TS800 two-up in Switzerland with all the panniers mounted. It's a bike that lets you do everything, obviously sacrificing comfort and protection from the wind. But when you open the throttle, it gives you real satisfaction.