IMHO I think Presti's going to have to face down a lot of "Draft the 'Stache"-type pressure if he's in a position to get Griffin. I personally think Thabeet would be the better pick, which is why he'd probably trade down if he got #1.
You have your SF/PF of the immediate future with Green and Durant. Drafting Griffin relegates one of he or Green to the bench, while still leaving a hole at center. I think they can afford to get Thabeet and use him like we use Oden (4-6 touches per game, if that) b/c they'd have Westbrook, Durant and Green all with the capability of scoring. Then you'd have a pretty stout defense with Westbrook, Sefalosha, Green and Thabeet all being primarily defensive-minded.
I know Griffin's the golden OK boy, and will be pretty good in the league, but for OKC? Not the best choice.