The MPK25/49 is nice... so is the APC40
Best thing to do is go to Guitar Center and play with a few. The last thing you want is to order something online and have it not be what you expected, quality wise.
Also, it helps to know what you're trying to do. Keys are always great because drawing in your notes can be a pain in the ass. Pads can be very useful too, as with sliders and knobs. It really depends on... what you're trying to do. Heck, you can use pads in a not-so-traditional way, such as triggering FX.
I'm a Logic and Ableton user. I've been using Logic since way back in the Logic5 days. I find myself doing most of my composing in Ableton and mix downs in Logic.
Oh yeah, the Oxygen8 is pretty good and cheap. However, I found that the less keys I had, the more frustrated I got down the road because I hated switching up and down octaves. It sucked when trying to actually play.