Both 6600GT & 6800LE support SM3.
[Generally you cant base how quick a card is in one game, as to how good it is.
Most people here state card A is quicker than card B & base it upon how it performs in multiple games. If card A is quicker than card B in say 60% of games only then its still the quicker card (provided it doesnt get blasted away in the games it loses in).
Do you have slides of how the cards perform in other games also?.
Also its generally a good idea to get a review from a couple of sites, just to be sure.]
However i thought the 6600GT was slightly quicker than the 6800LE, the reason some people recommend the LE is because you may be able to unlock some extra pipes on it, so then it would be quicker.