There has been a lot of discussion on this board lately about Cub's belt drive systems. It sounds like a lot of people here are unhappy with them. I have a 1046. My yard is mostly flat, but I do have some rather steep ditches in the front and back yard. I have only mowed with my 1046 once since I got in January, but there were no drive slippage problems and no lack of power problems. I may have problems later as I use the mower and it has some wear on it. But the design appears to work well for general mowing. There is a known issue with the drive idler pulley, but most Cub dealers already know about that and it is a pretty easy fix.
The main thing to remember is to use the machine for what it was designed for. If you plan on pulling or pushing anything, get a shaft drive, but for general mowing on most terrain a belt drive works fine. Cubs are priced very reasonably so you can get a lot more features for the same amount of money that you would spend on a lower end John Deere. I still don't understand why John Deere's are priced so high. I guess brand recognition is everything when it comes to price.
The best advice when buying a new mower, test drive a lot of different models and pick the one YOU like.