Revo 2s have been tweaked in the tread pattern to lessen road noise. Otherwise, everything is identical.
My brother works for Firestone and has had the Revos and now the Revo2 on his truck...he said there was no noticeable noise difference, but he has a Ram with a diesel so how much noise would he notice...
I recently replaced my Revos with another set. Firestone got me 4 tires rather easily but I really had to keep bugging him to get the fifth one in. He did beat the Tirerack clearance price though. If you can get the Revos they will probably at a reduced clearance price otherwise the Revo 2 are priced about the same as the original Revos were.