No, mental ray (3) does not seem to be P4 optimized. I was able to compare an Duron-1100 (Morgan-Core) with a Pentium4-1600 (Northwood-core with 512k L2-Cache).
In Maya4, which AW claims is P4 optimized, the Pentium4 rendered about twice as fast as the Duron.
In XSI 2 however (= mental ray 3), some scenes rendered faster on the P4 (but only marginally), but most scenes rendered faster on the AMD processor.
To sum it up, if you use Lightwave or Maya4, P4 is the better choice, because bot are optimized. But for mental ray, an Athlon is simply faster. The latest Palominos should be still faster than latest P4, and MUCH cheaper.
Andillo
