For InDesign (light graphics), RAM will be the biggest factor. The iMacs do have more in the power department though.
I think it really comes down to how long you are wanting to use them before replacing. Obviously if you are expecting 4+ years you will want the best you can get now. If you are like me and replace every 3 years, extra power is negligible cause they will likely be replaced before the software starts to max them (except for power users of course).
I think the question is to do what? Most users don't do anything more intensive than iMovie and PhotoShop. For them, and likely 90% of the users out there, the $599 mac mini with a $70 8GB ram upgrade (you need that) will be more than they ever need. Most people I know get hung up on the processor numbers and buy way more hardware than they need.
The bottom line depends on what your most intensive
application is. For instance, Photoshop will actually
perform better on a 2.7 dualcore that a 2.0 quad core.
Most of it's operations a singlethreaded (only doing one
thing at a time). But as an example, Hanbrake, which is
a video conversion application, will run 2 to 4 times faster
on a 2.0 quad core vs. 2.7 dual core.
The 2011 Macbook Pro line uses similar processors and
there are many benchmark reports for them.
The other item is graphics rendering. If you have graphics
intensive applications that are graphics chip dependent,
then you will want to opt for the Mini with the discrete
graphics option vs. the integrated Intel option.
I really really like the mini, but man I sure wish it came with four slots for memory so you could take it up to 16GB. I think the cpu isn't so much a problem for reasons other people have given -- especially when you run Adobe apps you can never have enough memory! I think the perfect app for that quad-core chip would be parallels virtual server, if it weren't for the lack of memory. I would run 4 VMs on it in a heartbeat except that you are only going to be assigning 2GB apiece...
I´m a graphic designer and now i´m using a new mac mini the "small one" with i5 and with 8GB of ram and is really fast. Lion only use 1gb of ram aprox, and 288mb for the video card.
I think you maybe need to know if the software you are going to use is really 64bits?? because for example adobe cs3 isn´t and it will only be able to use 3.5 to 4GB of ram (per application) i dont remember exactly the max of memory. The other thing is the weigth of the files.
The mini format also means mini power supply and mini cooling, so running graphics intensive apps, 3D (games) makes the mini run hot and the fan gets a little noisy. The mini is priced for what it is, a low end machine. Also make note of the max screen size in pixels and this may affect or limit your purchase of future monitors. And the 288MB video memory size is the minimum used, my 8GB mini uses up to 512MB for video. (World of Warcraft)
"The mini is priced for what it is, a low end machine."
I beg to differ sir. The Mac Mini is not by ANY means a "low end machine". It may be the lowest end between the Mac Mini options but consider the price when it doesn't come with a monitor, mouse, or keyboard... If you were to compare this to a mid range iMac the pricing would be equal once you added the missing components.