What's your maximum budget?
Personally I prefer the print quality from canon and the finish from xerox; I've had some great ricoh b/w machines but I haven't seen top-end graphic color from them.
Have you requested and looked at the print samples already? That's the only way to know for sure if the print quality will be what you're after (many like the punchy color from xerox for example, but I prefer the more subtle, I believe realistic and offset-like, colors and gradations from canon machines in general.)
Once you settle on the mechanics, the rip will also make a big difference on the subtle smoothness of screens, gradiations, speed, and color management.