As the title asks, what would be a deciding factor between going with a iMac and the Mac Pro?
Im getting a bit lazy I suppose and am tired of lugging the MBP home nightly from work and am contemplating options. If it would be an iMac it would have to be the 24 inch version as the screen on the 20 drives me nuts and I already have a great 23 ACD so the screen isnt really my driving force here.
You don't seem to give many details on what the system will end up doing. Will you be using it for your work? What will that be doing?
Personally, I have the 2.8 iMac. Its a really great machine. Depending on what you use it for however, you will very possibly have to upgrade the memory. This will ring true more so if you use design applications like Photopshop, Illustrator etc.
I am currently a final year design student myself, and have found that Photoshop (CS3) is quite the memory hog, much more so than any other application I run, taking up a whole gig by itself at times, so the 4GB upgrade should be considered in your thought process.
The fact that the iMac is a closed system is defiantly a down point, as you cannot upgrade the graphics card. This is something I dearly miss and would be the biggest, if only downside to the iMac. This is where the Pro would come in. With totally crazy prices however, you really would have to have the need for one of these machines, to properly justify buying it. Either that or you have the extra cash to spare, and you would like to treat yourself.
So it all comes down to what you are using the machine for. I would naturally recommend the iMac, as I cannot see you needing the performace of the Pro. I really think it will match your needs, and fit into your lifestyle better.
Hope this helps.