Ok, it depends on what I wanted to do with it!
I'd use a different board for APV vs. sport flying and potentially yet another one if all I had in mind was flying FPV.
Or you could just do like I seem to be doing lately and buy at least one of each type and build a frame to put it on. So far I have three different flavors of KK, no wait, make that 4 now, two MK FC 2.1 flight controllers with full GPS and Navi stacks on top of them, a Hoverfly Pro and a Hoverfly Sport, a CC, a Quadrino, and two Gaui 344 boxes. I think that's everything though I might have missed one or two that are currently stuffed in a box somewhere...
For me the MK are primarily APV use, the Hoverfly Pro pretends to be pro level APV but the reality is it isn't quite ready for prime time though it makes a darn good FPV board if nothing else and has the bonus of being able to handle a 2 axis camera mount fairly well at the same time.
Hoverfly Sport is for sport flying and I think it's an outstanding all around and backyard just fly it for the heck of it board that will do aerobatics if you're up to it. The KK are now fairly obsolete technology but the more recent ones make great aerobatic controllers. With the advent of Mike Bartons C code programming for them they are making a bit of a comeback with some advanced capabilities like the Mems gyro/GPS add-on board that Minsoo Kim has developed.
The newest versions of the Multiwii variants are getting quite plug and play as opposed to the build it yourself original versions, the Quadrino being one of the fully assembled, plug it in and fly variations with PID loop tuning capability via Gui. Useful for sport flying and FPV thanks to autoleveling, altitude hold, and mag abilities the Multiwii mimic the capabilites of some of the much more expensive boards at a fraction of the cost, generally from $100 to $150 US. Downside to these boards is you need to be a hands on type with software loading and tuning to get them to fly well, if you're comfortable with that then these are a great alternative to KK boards.
The CC IMO is inline with the Multiwii boards in terms of capability and tunability although I think the CC is a much better designed board which it should be as its purpose built rather than spawned from an idea to build an FC board from a bunch of somewhat unrelated components as the original Multiwii were.
As for the Gaui brains, what can I say that hasn't already been said! I will say this, the Gaui 330X is probably responsible for a very large number of new pilots getting into the multirotor end of the hobby as well as converting a few RC Heli pilots to a better way as well (raises hand). Not the steadiest or most robust controller to ever come along but very simple to get in the air and learn how to fly, I still have my original 330X, pre S type that I fly out in the backyard when I just feel like getting in a little stick time.
That pretty much covers my inventory and its barely a fraction of whats on the market now so lets hear about some of the other boards from the rest of you.
Ken