Having a 25-note keyboard can be really limiting if you're trying to play anything complex. You can get by with a small keyboard if you're just doing simple basslines or melodies, but if you're doing really dynamic music, playing two-handed chords, or anything else that requires more than 25 keys, you're screwed. It really all depends on your keyboard playing level and whether or not you like the feel of the keyboard. Most cheapish midi controllers have really spongy action, nothing like a piano. If you want the drum pads (which I hear suck), faders, etc... get the MPK. It has some nice features, but if you merely want a controller that feels good and isn't limiting, get something with 61 keys and a weighted or at least semi-weighted keyboard.
MPC 1000 w/ JJOS - Korg ESX - Korg EA-1 - Ensoniq EPS 16+ - Waldorf MicroQ - Roland Alpha Juno 2 - Yamaha TX81z - Mackie CR1604 - random rackmount and pedal effects