Mac Pro is better, simply because it allows you to add more hard drive space internally, etc.
The biggest reason is ram, you can extend over 16gb of it, something graphic designers love, well .. photoshop loves ram actually.
And the mac pro has 2 cpus, and not just 1 with multiple cores. The performance is noticable when you do serious work with the breast.
The iMac is great, especially because of its bigger screen, you can place it almost anywhere in the house, but it's not something you can take with you. Unlike the mac book pro, which in my opinion has the same performance, they both come with 4gb of ram or more, and have option for display port, to second monitor, and dual or even quad core cpu's.
Don't get a Mac Pro with 1 cpu, kinda defeats the purpose.
It just depends on your budget, what you think you need performance wise, and how you want to work.
I consider for serious video and photo work to get a mac pro, it gives you the freedom to easily replace hard drives, make proper back ups, get beast performance, and replace broken parts. And you can add multiple video cards to have multiple monitors (crt, 4:3, 16:9 and 16:10 and different sizes).
Sorry.
mx revolution ftw.
