I dunno....its a good question.
Well, in my opinion, the RAF is the best.
In terms of combat experience, you gotta pick either the USAAF or the RAF. (just opinion, am always open to new insights...so please update me whenever you wish)
I think its the RAF, thanks to their new Eurotyphoon fighters....I love that plane....
and since the USAAF still hasn't replaced their airfleet of F-16s and F-15s with the new F-22 raptor, (i heard that they are actually going to adopt a cheaper version of the F-22 called Y-22 or something (da hell...))
anyways, since the Eurotyphoon is currently one of the newest fighters in the world, and since France, Germany and Spain isn't included in the list....I go with the RAF. Its just in terms of technicality....there are probably a lot of better airforces in the world, based on training and pilot capabilities... but ill just go with the RAF....