I've been using a tower for a while and I like it for all the usual reasons, expandability, the PCIe slots, extra hard drives, etc.
At the same, it started to piss me off. My tower pissed me off. I’m not one to get emotional about my equipment, ever, but I started to f*cking hate my Mac f*cking tower. F*CK!
So I up and got an iMac i7.
I have both now, and I’m in the process of migrating my recording to the iMac to see how it goes. I guess I could always go back to a tower if it didn’t work out – not this one but one that had a bit more juice and made a bit less noise.
I haven't really put the iMac through its paces so I can’t really say much about it other than so far, it’s a beautiful beast of a machine.
So first of all, I would have to advise you to get the iMac i7 because recommending other people buy what I buy helps me justify my own purchasing decisions, and by extension validates my existence.
Having validated my existence, it's hard to say.
The iMac is a lot more affordable and clean once you add up all the things you'd have to buy with the Mac Pro. The tower, at least mine, can become a growing mess of crap, and you have to add in all the costs of all the stuff you add to it. Maybe I’m fooling myself that I don’t need all of that, but wouldn’t it be great if I didn’t? With the iMac i7, it seemed worth a try.
However, if you are going to require several hard drives with simultaneous high performance connections, or if you require the flexibility only a tower can provide, or are willing to pay a premium for what may be an incremental advantage, then you might want to get the tower.
Hell, if it turns out my iMac isn't doing it, I'll go back to a tower. But I’m really hoping the iMac works out because it’s such a beautiful beast of a machine.