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?
The new iMac is probably the better machine than the two-year-old 6-core Mac Pro, except for the notable fact that Apple says the iMac is limited to 32 GB of RAM. (OWC will sell you RAM bundles for either machine that are larger than what is officially supported.)
I'm not sure what "extremely large and complex" means to you, but I wouldn't consider either of these machines for regular large-format work because of the RAM and CPU limitations.
Generally, I don't think the overhead of network rendering is worthwhile with only two nodes.