Greetings all, I would like to solicit your professional opinions.
I am currently editing on an iMac 27" Retina 5k, Late 2015, 4gHz i7, 32GB 1867 MHz DDR3, 1TB SSD, AMD Radeon R9 M395X 4096 MB. This machine has Thunderbolt 2.
I have the opportunity to take over a departing colleague's machine, which is an iMac 27" Retina 5k, 2017, 4.2 gHz i7, 16GB 2400 MHz DDR4, 3TB Fusion drive, Radeon Pro 580 8192 MB. This machine has Thunderbolt 3.
I can probably upgrade the RAM to 32GB, for the second machine, and I edit on external thunderbolt SSDs.
Both being fairly equal, because you won't notice the .2GHz CPU increase, the 2017 has faster RAM, which you will notice in overall system performance, as with the increased GPU VRAM. Only downside of the 2017, fusion drive. I'm not crazy about them. But considering your Libraries and media will all be on a fast external drive, the fusion drive won't matter. The 2017 would be enough of a bump to make it worth while, IMHO. A T'bolt 3 RAID would be icing on the cake.