Yeah, cos for my CAD workstation I really want to be using an aesthetically pleasing Mac, instead of a fire-breathing badass quad-socket 24-core PC.
this... seriously just go with the pc, easier to use if every aspect that you would need a computer for.
i scoff at noobs who buy macs becouse there "cool" seeing there paying over a grad or more (depending on the model) just to surf the internet and use its webcam.....i know some people do buy them for editing purposes wich i can see, there a decently beefy computer for what you pay for and thats one thing macs are specified for....buisness.
Keep in mind that an iMac is basically a really big laptop that needs a power cord all the time (do they use desktop CPUs or laptop ones like a lot of Windows all-in-ones?). They are designed for casual users who require occasional spikes of processing power. Like a laptop, they suffer from crappy ventilation etc because they make sacrifices in the name of looking pretty.
If you're going to be doing sustained high load work (for example video editing/encoding) you need something designed for this purpose. There's a very good reason a Mac Pro looks like a regular PC, just with a brushed aluminium case.
You wouldn't buy a Ferrari to tow your boat. It might look nice doing it, and no doubt it would probably tow your boat pretty damn well, but it would last about a week. Same thing here.