Looking for some advice. I have been debating on whether to update to a maxed out iMac 5k or a 6 core Mac Pro. I'm editing on a daily basis using premiere and after effects but only in HD, no 4K. For this type of work, the iMac should do the job just fine. My dilemma is that a work on a few extremely large and complex video wall presentations every year in after effects that require massive compositions, long render times and transcoding. Should I spend the extra cash on the pro knowing those projects need something more powerful than the iMac? Should I consider getting the iMac and using an older 12 core Mac Pro I have for these intensive projects. Maybe consider network rendering between the two?
You might want to ask this on the Adobe Premiere Pro or After Effects forum to get advice from editors that actually use the software you are using. I don't use either (I use Final Cut Pro X and Motion).
I agree that heat could be a problem with an iMac for long renders in which case I would get the Mac Pro. I recently purchased a 2010 12-Core Mac Pro instead of the iMac 5K for the exact same reason. I wanted to be able to do long renders without the worry of heat. The 27" iMac with Retina 5K is an absolutely gorgeous machine and I seriously considered buying it and people who have bought it say they love it. If you have an old Mac Pro just for the occasional long render, I would go with the iMac 5K for every day use. If you stop by the Apple Store to see it in person, you'll want to buy it. It's very impressive. ;-)