It all depends on what you're running. OS X would make heavier use of L3 caches because much of the code is larger. OS 9 typically is fine with the 512k of CPU speed L2 cache on the 7447a cards. Of course, if you can get 7448 cards with 1 meg of L2 at CPU speed, that'd easily be much faster than the 256k of CPU speed L2 and 1 or 2 megs of 200 - 250 MHz L3.

I have a 1.733 GHz 7448 on an older 133 MHz SDRAM bus which is noticeably faster than a 1.8 GHz 7447a on a 333 MHz DDR bus.