I used to raid/pvp in wow pretty aggressively. Personally, I'd say go with the browns if you're deciding between reds and browns. Most of the time if you're queueing spells you're going to be spamming your rotation, and with reds bottoming out the way they do, you'll lose a lot of time until you get really used to the point of activation. Alsoreds are more of a pain to type with (which is as relevant in mmos as it is in anything else). Browns more mimic the way standard keyboards work, with a tactile point of activation, but they are probably slightly louder than reds, if you're touch-typing.
I'd probably even go with blues before reds, personally, as I think linear switches are a large jump from any tactile key (which, never having a mech keyboard before, you're more used to). If you ARE serious about trying reds, I would say try before you buy. Usually a best buy or somewhere similar will have a few keyboards out to test...and getting even just 10-20 seconds with a set of red switches will tell you what you can expect.