1. The 2250xp is a pretty serious machine and it was designed primarily for the stump grinder beginners and the rental market because of the ease of use and low maintenance cost. It run around 17,000 bucks. You really can't compare a belt driven machine to a hydrostatic drive machine. The way hydros are design their will be a slight power loss. The main point in using a hydro machine is the ease of use and maintenance cost. Don't take me wrong, there is nothing wrong with the belt driven machines. They operate and work very well. What will be the determining factor as to which one you end of getting is; you have to answer this personal question "whats in your wallet?"
2. For now the 2250 will only come with the 27hp kohler. If you want a bigger engine you will have to step up to the 2550xp which will be hitting the market soon and a variety of engines will be offer on this machine. Of course it will cost more money to purchase. Look for bandit to offer the 35hp briggs & stratton, 38hp kohler, 35.1 kubota and the 44.2hp kubota.
I spoke with a bandit rep yesterday and we had an extensive discussion on the NEW HYDROSTATIC DRIVE stump grinders. This link will give you all the spec on the 2250xp:
Bandit Industries, Inc.
This link will give you a video of the 2250 in action:
Bandit Model 2250 XP Hydrostatic Direct-Drive - YouTube
I hope you find this helpful and take care