I'm not an expert in this area, so it's hard for me to tell between the GPU and CPU which plays the most important role. Perhaps it's dependent on the way the software is written, I'm not sure. However, as I've read through the threads here I've noticed some discission of difference in times, but I can't tell why. For example: Mac Pros are beating out the iMac, which in turn beat the Mac Books. Now I know this may seem obvious and "duh", and more is better, but how much more and what is it worth - both in terms of dollars and time? Let's assume the processor speed is the same, what benefit would one see from the 256mb iMac card v the 512mb card? What then if you bump the processor to the 3.06ghz option? Likewise for the new entry Mac Book with the 9400M to the dedicated 9600 unit.