I know this thread is pretty old, but for what its worth, I recently bought both a Behringer BCF2000 and a Korg NanoKontrol2.
Both have similar overall functions, but the BCF (@ ~13"x13"x3") is quite a bit larger than the Nano (@ ~13"Wx3"x1").
Usability: The BCF2000 has a lot more room to use the individual buttons and sliders, so it is a bit easier to make very fine adjustments. It also has motorized faders. I use it to control the intensities of submaster channels, so the BCF console echoes perfectly what is shown on the touch screen. I had to modify a couple buttons so that they would work on a single-press, rather than sending a separate ON and OFF. (you can see how to do that here:
viewtopic.php?f=19&t=2958)
The Nano is so much smaller that it initially feels like it can't do the job, but I've found that it performs really well. The Korg is able to do everything the BCF can do, except it does not have motorized faders (but that's not a deal-breaker for me). Additionally, Korg released is a free software program called Korg Kontrol Editor that lets you use a simple graphical interface to modify how the buttons, faders, even how the LED lights on the Nano function. This made it extremely simple to customize the Nano for Freestyler use. No programming stuff in MidiOx!
Ultimately, I had members of my lighting team experiment with both the BCF and the Nano, and they unanimously chose the Nano. It is so much smaller that it can easily sit on a little panel on top of the ETC Express console (that was the original controller, now only used for backup).
Hope this helps if anyone is researching whether these devices can work with FS.