Is there a comparison between the different MPC models?

What up....I am thinking about buying one of the MPCs, most likely a 1000 but possibly a used 2000xl or maybe even the 2500. Does anybody know a place where I can easily see a comparison between the different models, to determine which is the best route to take?

Also, how do the MPCs usually hold up on the used market? I don't want to get some messed up pads, a bad screen, or a screwed up output...

Thanks for helping me out.