Memory is critical. Poser eats a lot; a moderately complicated scene can easily take well over 1Gb to render. Whether Windows or Mac, the system is using a fair amount of memory already, and even if you have 1.5Gb Poser is going to be paging a lot. That slows things down immensely. Better paging helps; and that means Mac OS X is better than Mac OS 9, Win XP is better than Win 98; etc.

Right now, for example, I happen to have a render running behind this browser. Mac OS X 10.3.4, dual 1Ghz G4 with 1.5Gb. Poser is taking only about 89% CPU (and despite not being explicitly multiprocessor-aware, that's NOT all one CPU, because some of the OS subsystems Poser uses are threaded), and there's idle CPU time on both processors. In other words, a faster processor wouldn't make much difference. But Poser's total virtual memory is 2.55Gb; of which only 940Mb is in physical memory; there are virtually no free pages. (That's with 4 Vickis and a global lighting setup with lots of lights.) The system is averaging a couple of hundred pagefaults (meaning something needs memory that's currently in a paging file on disk) every second; and probably most of that is Poser. It adds up.

Any graphics application is going to eat memory; but some, like Photoshop and various high-end 3D apps devote substantial engineering time to optimizing their memory management; knowing that it can make a big difference in performance.

If you want Poser to run faster, more memory is probably going to help a lot more than a faster CPU. In this particular case, if I had 2.5Gb free physical memory, I suspect Poser would be waddling along sprightly enough. (And once you get rid of the paging, THEN you may well find that a faster CPU will help even more... but I'm holding out for the 2nd generation G5s ;-) )