Two macs. Which one for CS5 & Logic

?

Are you running plug-ins/VSTs? (Reaktor, Amplitude, etc.)
How big are your photos?

The newer i7 architecture will (I think) be faster for non-optimized programs such as plug-ins, etc.
However, the increased RAM and HDD Capacity/Speed (15000RPM or, potentially, RAID configuration) of the Mac Pro would make it much better for dealing with very large projects, such as high-megapixel RAW, extensive audio sample caching/playback, etc.


I think either way it is a quad-processor (i7 is quad-core, no?), so how big (sample and mega-pixel wise,) are your projects and do you want to use your own 2 screens?

Personally, I've run into no major issues doing DAW work in Ableton with fairly extensive plugins on my C2Duo Macbook Pro /2GB/5400RPM, so I would think either would be fine. Using Apple's high-glare screen such as the iMac has for extended visual work is quite annoying, however (imo). I would get the Pro with 2 nice S-ips or IPS displays.

 

It's hard to say. There's is no i7 iMac in a base configuration, so which one are you looking at? How much RAM and what kind of hard disk?

I think the Mac Pro will probably be much faster. It's got dual quad core Xeon's, eight cores if they all work plus a heck of a lot more ram. It's probably faster RAM and a faster hard drive too. The only thing i would recommend is a better graphics card for general performance, although I don't think it'll matter so much for photography since the processor is so high end.

 

long in the tooth

That graphics card and processor suggests it's a Mac Pro 1,1

You should be able to get a much better/more recent Mac Pro for the same money as an iMac i7.