I have to give a vote for browns, or a custom setup with Sanwa arcade buttons. I play quite a bit of stepmania, the ddr-clone on pc, and I had huge issues with blues for quick repetitive taps, but no problems at all with browns. I can't speak for blacks, but they take quite a bit of force, I ruled them out as probably too tiring for regular use without even trying them. I'll probably pick up a cheap black board at some point just to see what I'm missing out on, but I don't see it replacing my filco with browns.
As for Sanwa's, you could easily fab your own controller up using just the pushbuttons, it shouldn't set you back much at all. I've never tried gaming with the 24mm's, but the 30mm's are absolutely amazing, assuming you don't rest your hand on them. They really do activate with almost no force, you can look at them cross-eyed and get a press. They've got VERY little travel, as well, which makes them ideal for something like this.