With so many on the market, it gets overwhelming when choosing a midi controller. I tried to give a honestly and useful opinion when this question was put to me.
As you can see below, I have 4 controllers all of which do different things to fix certain needs. The largest one is the M-Audio Ozonic which is a 37 key midi controller which has buttons, faders and a built-in soundcard with phantom power so that you can plug in a condenser microphone.
The other three MIDI controllers (made by Novation, Korg & Akai) are all 25 key, which still allow you to connect to a laptop computer and give you all the functionality of a bigger midi controller. Not forgetting they’re great for travelling. They are really handy to put in your backpack on the go…
So really, ask yourself what needs are you trying to satisfy and do you have the space or do you not have the space or do you need functionality with mobility?
Hope this helps!