I would personaly pick the 66! it can be used for FR and DH no problem! On the other hand, the SUPER T is a good fork also.. DEPENDING ON the year. Ive owned 2 supers and 1 66 before. You have better adjustments with the 66, then the Super T!
The 66 will have a better dampening system than the Super T. You will have to specify what year and model you're thinking of. I'd take a 66RC2x '06/'07 or RC3 '08 any day before touching a Super T. But if you're thinking of a newer Super T vs 66 '05, I'd rethink it.
Granted the Super T is a double-crown fork. It will give you a (very rarely used) slightly better turning radius, and it will probably be stiffer. I have no idea, I've never tried a Super T. But what I do know is, my 66 is plenty strong for all my 165lbs can throw at it. Axel-to-crown length will differ from year to year too, so you'll have to specify that.
Conclusion:
'05 66 vs '06 Super T = Super T '06-'08 66 vs any Super T = 66
yeah there both good, I'd personally go for the 66, it opens up more possibilities, it LOOKS lighter dont quote me on that, and its a better quality fork