I'd go for a reference board because they dump hot air outside the case. The other designs just recirculate hot air. Reference boards have a centrifugal/exducer-type fan at the very end of the board.
Have you ever owned a 6950 or 6970? The reference board is garbage. There's a reason every single manufacture went with a completely different cooling design. Also most of the reference boards don't pipe it out the back, they pipe it out the side which still goes right into your case.
I bought a few 6950 ref boards and unlocked them, honestly I wish I would have just purchased non-ref 6970s. They produce so much heat, the design is awful, avoid reference cards as a rule of thumb unless there's some unlocking that makes it worth the trouble. Having a sealed case where air is pumped through the case sounds good, but that sealed case also means if you put a fan on it you're just hitting the plastic shell and not cooling it at all. With the more open dual fan design you can at least help cool the heat sink and pipes with more fans.
Also the reference fan is freaking loud. Way too loud. I can have 3 5870s running, 1 6950 and the 6950 is 3x as loud by itself. I'll never buy another reference board I don't care if I can unlock it for 20% gains or not. They're hot, loud, poorly designed.
As for the best, go by the number of reviews and the % of 4-5 stars. If one card has 200 reviews at 70% I prefer that over a card with 10 reviews at 80%. Get a popular card, with good reviews, and you'll be fine. If noise bothers you, read over the cons looking for complaints about noise. Newegg reviews will pretty much tell you what you need to know if you read enough of more. More reviews the more you can trust the ratings. Less reviews a little more risk.