Ask Max: Is there much of a speed difference between dual 2.66 and the dual 2.93 GHz Nehalem Mac Pros?
I'm interested in a Mac Pro for heavy Photoshop graphics use. Is there a noticeable speed difference between the dual 2.66 and the dual 2.93 GHz units?
With the 2009 Mac Pro, I do not think it is going to be too noticeable of a difference in the single processor (4 Core) systems. In the Dual Processor (8 Core) Systems, there is a considerable difference between the 2.93 and 2.26 models. Look at these charts from Bare Feats' Nehalem Mac Pro performance tests.
This should give you some idea of the differences but there is no surefire way to determine how your workflow will ultimately perform. Get as much as your budget will allow, but make sure you have tons of RAM as part of the config. Always bet on RAM :)