Resolume's MIDI mapping is very intuitive, so I would think a bit about what you need, and your budget. For example:
1. VJing with BPM sync/many clips: I would look for something with many buttons (e.g. Novation Launchpad)
2. Corporate gigs/scenic design, with more fades/column triggers: you mostly could use sliders (e.g. Korg nano series)
3. APC40: I love it, best of both worlds. You can trigger clips/columns with buttons, fade in/out with sliders, control multiple decks, and effects (I put them on layers). There's a great deal of support/documentation on this forum for this model too. It's a bit expensive, but for simpler gigs there's also the APC mini.
Also, if your budget is in APC range, check out the Livid MIDI controllers. They are beautifully designed and crafted, and are fully customizable (in case you don't like all the controls being labeled for Ableton functions on the controller itself).
Just my $0.02
I'll leave this here : http://controllers.cc/
Your controller should have the knobs, buttons and encoders you think you need.
It highly depends on your desired workflow imo.