I have the APC 40. the apc is nice, but it's limiting only showing 4 rows down. I've found myself using my mouse even with all those options to be completely comfortable while trying to express a live pa. apc is also nice to use while writing tracks, giving you endless assignable knobs, fader, crosfader.. ect. using the faders is really nice feature for your mix downs, giving you even that much more flexibility.
If you don't have a midi controller for a keyboard, then the MPK25 would serve a dull purpose. Personally, I just got rid or removed my smaller midi controllers, and use a traditional keyboard. I just recently just came to the conclusion that writing using a full size keyboard was that missing feeling that left many years ago. so it's nice to get these all in one controllers, but at the same time they are some what limiting.
if you don't have any mini controllers with a keyboard option then the mpk 25 is a nice start, however with a stripped down version of what the LPK25 provides, would then allow you with $140 towards a apc 40, which is tailored for ableton as well. just meaning perhaps consider getting a basic basic midi with keys first, then when you do spend the money you thought you would, it would be on something customized towards the apc. Not an "all in one" which the markets are creating out of convenience with a little lower price for appeal.
just something to consider.