I have both and can give a fair assessment of them.
The PQ is a dang good reel. Built like a tank and keeps going and going. There is a thread here http://www.bassresource.com/bass-fishing-forums/topic/112219-bps-pro-qualifier-bc-reel-%E2%80%93-5-year-challenge-%E2%80%93-time-to-pay-the-piper/ that breaks it down and one heck of a test on it. The Pro Qualifier has been around the block for some time and has proven its self. Bass Pro changes these up from time to time and from what I'm told, this model has been the same for the longest time. The PQ has a dual breaking system. You can fine tune it to whatever situation you need. For me, I don't use the mag breaks at all so its a mute point. The PQ is a great price. Its going to be on sale on the 22nd of this month too. The down side of the PQ is the weight. Its kinda heavy. You can't go wrong with it. It comes in 4 different gear rations for any situation.
The Revo S (Gen 3) is a whole different sexy little hunny. For the price point, its the lightest reel out there. I love mine. Very smooth and sits super low. The Revo S has a 6 pin breaking system like the PQ, but does not have any mag breaks. For me, that's a plus. The Revo S has only been around for about 7 months now so its still proving its self. Only time will tell. The S only comes in one gear ratio, so its kinda technique specific.
Hope this helps.