Along with the higher "duty cycle/recommended monthly volume" posted by
@namelessentity , the Versant also handles higher gsm (400 vs 350) and it's faster (100ppm vs 90ppm). Even though you may not have a need for 400 gsm currently, you may in the future...either way it means it's built more robust to handle the heavier weights that you do regularly run. 10ppm won't make or break a deal for most people, but it's just one more benefit if both vendors are offering you similar deals.
I agree with the others that I've always seen the Cx10 series from Canon as a step just above their office line. One clue is to look at the amperage required by the two machines. The C910 is only 20A, while the Versant is 30A. The Canon C10000 is more in line with the Versant 4100, if not a step above.
The biggest consideration that I always tell everyone regardless of which brand they choose, is to verify what service for that brand like in your area. You already know what Canon's service is like, so you'll need to investigate what Xerox is like beyond what the sales rep tells you. Be careful asking shops that have Irridesse's or other similar machines, because those get a higher level of service and response time than the machines like the Versant and below.
Lastly, whichever one you get, if you're going for the Fiery controller, make sure you get the higher end Fiery (with FS-400 Pro). So many people try to save a few bucks and get the smaller Fiery, and regret it due to how much slower it is with processing files, especially variable data.
