As to which version of the K70 RGB I don't really know.
As far as which switches, I have used red (K70), Blue (Razer Blackwidow Ultimate 2013), and now the K70 RGB with Browns.
I found the reds to be incredibly annoying to type with, often accidentally pressing a button. Shorter key actions do give you a slight advantage when having to react quickly in games.
The Blues were amazing, if you like clickiness of switches then look no further. Only problem with it was that it's loud... VERY loud. I have litterally woken up people from typing on it. Surprisingly, gaming wasn't half bad either.
Now I've been using the Browners for a few months now, and it's basically a quieter version of Blues, which is a good thing AFAIK.