Definitely interested in your results
I was able to spend a bit more time today running comparison tests using a few real-world projects from my recent work, in both Premiere and After Effects. The TL;DR version is: I'm probably going to keep the 16" MacBook Pro (M1 Max) and sell the 2019 Mac Pro.
The most comprehensive test I ran was in Premiere Pro. It was a multi-cam edit of a concert we shot just before the pandemic. Six cameras (with some mixed formats/codecs) and some color grading. Exported in H.264 1080p. The Mac Pro took 21.5 minutes. The MacBook Pro (M1 Max) took 18 minutes. Not a huge difference, but considering the Mac Pro had edged out the MBP in the shorter, social media video export I tried the other day, it wasn't the result I'd expected.
A second test with another multi-cam edit (just four cameras) bore similar results. One thing in the Mac Pro's favor, when viewing all of the cameras side by side in preview, all streams were consistently smooth. There was one moment when the previews on the MBP stuttered for a few seconds before smoothing out — but it wasn't significant enough that it would be problematic while editing.
I then tried some tests with After Effects, where my results were also a bit different than the quick and dirty comparison test I ran the other day. This time, I decided to completely ignore export time, since it represents only a tiny fraction of the time I spend using AE. I focused instead of timeline playback/rendering. On a few different AE projects (using Video Copilot's Element 3D and some of the plugins from Red Giant VFX Suite), timeline playback was pretty much the same on both machines (i.e. pretty painful). I did note that turning ON motion blur would hammer the MBP, and the Mac Pro would pull ahead significantly... but it's easy enough to toggle that setting while working. In several different compositions I tested, neither machine could do realtime playback, but with motion blur turned off, the MBP would get through the timeline consistently ahead of the Mac Pro and loop playback smoothly via RAM preview. I guess the (wholly unsurprising) story here is... the plugins/effects you're using will make a difference in one direction or the other. For my purposes, I guess I would call this a wash.
BUT... though I downloaded the beta version of After Effects for Apple silicon, there are a significant number of built-in effects that just don't work yet. And none of the third-party plugins seem to work at all. Which meant that I couldn't test any of my projects in the beta. The fact that AE is running on the MBP (via Rosetta 2) pretty much on par with the Mac Pro, though, leaves me hopeful for a fully-baked version of After Effects for Apple silicon.
Anyway. Take this all with a grain of salt — I'm only considering my own use cases. I wanted to make some observations comparing the two computers using files and scenarios that I personally encounter all the time in my day-to-day. For me, at least, the two perform
very similarly, so I'm giving the nod to the MBP, just for the portability and lower power consumption, since the Mac Pro's expandability isn't critical for my needs. ymmv