It depends on what you mean by 'best'. Best purchase? Best in terms of power/cooling?
I tend to stick with eVGA for nvidia, and MSI for ATI/AMD. Simply because I have purchased these respective cards from those companies in the past and have never failed on me once in a decade.
They have both, in my past experience, overclocked well (towards the higher end of the OC spectrum in the evgas case, but the ATI/AMD still overclocked), definitely within what you expected to get out of it. In the eVGA 88GTs case even a bit more (got it running at factory superclock speeds having bought a regular).
To boot, eVGA is my absolute preference, as they come with a nice handy lifetime warranty (just make sure you register the product!). They honor it too: my 88GT died this passed January after 4-5 years of solid use (OC'd too), and evga sent me a new one, which I got VERY promptly, alls I had to do was pay shipping. Theres even a special shipping you can get from them for like 5$ more so that they send you the new card FIRST and THEN you send them the old card.
Idk thats why those would be the best to me. Reliable hardware, overclock fine, lifetime warranty (in evgas case), and the stock cooling is not to shabby in eithers case? Sound like winning brands to me.
I stick with evga when I can though. It is always SO NICE when in 5 years and youre still using old parts (on either your older rig or simply because, like me, you have yet to build a new one b/'c of time/$ constraints, etc), and it dies, to not have to worry about dropping $ to fix an older, aging rig. I mean shoot, after 5 years I dont want to pay for a new 88GT, i want to save my $ to put towards a new build. SO! that lifetime warranty adds somewhat of a financial cushion, in theory.
Not to mention its a good resale point: I'd MUCH RATHER buy 2nd hand evga parts that have been registered and a transferable lifetime warranty. Meaning if you buy a used eVGA part the owner can help transfer that warranty to you, so if it dies for whatever reason you STILL get it replaced; which is awesome with used parts if you consider the implications of that. So if the seller was less than honest about the true condition, or if there is a defect that finally becomes apparent with use in a new system, you are not out the $ you just spent on the used part.
So yeah, that lifetime warranty IMO makes a used part all the more attractive.
As I said, Idk whether this is the type of answer you wanted, or if you want actual numbers and varying degrees of temperatures with the different coolers. But honestly, most stock coolers are basically the same, maybe vary a bit depending on the manu, but usually keep the cards w/n a couple degrees of each other. One or two of the pack MIGHT be super loud for whatever reason, but again, all usually w/n a few dB of one another. SO to me, more important is reliability and integrity, as I can always add a nice after market zalman for not that much $ if i really need the cooling/noise reduction.
Edited by kmac20 - 7/22/12 at 9:43am