In my experience I've found that the 'best' kb is what you're the most used to.
I've tried several over the years and my favorite kb ever was a thrift store Gateway or Dell kb ($1, can't remember brand) with membranes. It fell apart after a year of playing but it was better than my K70 that I have now when it comes to roping. I'm not going to bother having multiple kb's for gaming. I've also never noticed any real difference between USB and PS/2 keyboards, although I know on paper that PS/2 is supposedly superior. Also, lots of people (including myself) play via laptops, so USB is practically a requirement. Now that I am used to them, I greatly prefer mechanical kb's for the overall feel, gaming or not.
As long as the kb is full size and doesn't have keylock, anyone can get good at using it for any scheme. The main advantage IMO that 'gaming' kb's offer is that they tend to be of a higher construction quality and last longer. I barely play W:A anymore due to being in and out of the hospital but this K70 I have has been used extensively for quite a period of time and it doesn't show any signs of wear aside from just being generally dirty. I don't remap my keys and my spacebar feels exactly the same now as it did the day I bought it.