Hiya,
I had a 2520 and never found it lacking for power for cutting or tilling. My opinion is that the 2520 has too much power for the weight of the chassis. In ground engaging work, (loader, ripping, plowing, grading etc..) the tractor would slip it's wheels far too easy. (and this was after I loaded the rears, put wheel weights on, added 3 suitcase weights on the front and a portland weight box with four 40 lb suitcase weights on top)
If your mainly going to cut or till and you want the extra PTO HP, then the 2720 may be a better choice however if your mainly going to be doing ground work, the 2520 will be more HP than you need in that chassis size.
If your planning on mainly ground work, you may want to look at the 3x20 chassis size. They weigh far more, have 3 ranges in the hydro, have much higher loader (300cx) and 3pt capacities and can put all the power to the ground with no wheel slip. After 4 years with my 2520 I went to a 3320 and haven't looked back.
My 2 cents,
Tom