They are identical units in terms of processing power the only difference is the screen real estate and vid card.
maybe a macpro would be more up your alley? I know the imacs are pretty good, but i would think a mp would be balls out faster than the imac for what you are describing. also, if you're maybe thinking of video editing..maybe get the machine that will be faster if you need the speed later. just a thought for looking ahead.I am a photographer and I will be using Photoshop and I think in terms of power tools that will be it...maybe some video editing and gaming so for the people that know both imac does the large benefits of the 24" amount to me getting the 24" over the 20" or is the power of the 20" more than capable....
I recommend the 24". I use Aperture and Photoshop and also went through the decision process, 20" or 24"? I am soooo glad I went with the 24" iMac.Size matters.