I've got a slight follow-up to this. I'm still looking into this matter (how could I let go of that much of a gain in render times?!) and what I've gathered is that AE doesn't utilize the GPU at all while ME does. I'm having a hard time believing that this is the explanation for why the same exact composition renders faster in one over the other.
I'm going to have a chat with myself for a little bit.
So I did my own monitoring of system resources. In both AE and ME the GPU is essentially not active. The CPU is at around 25% for AE while it's at 45% for ME. So this seems to be a new sort of problem.
Remember that AE CC 2015 is still a work in progress when it comes to rendering.
Adobe's AE team is working to increase overall efficiency & speed in AE. Because they had to meet a release date that included many other applications for CC 2015, the team picked a stopping point.
The work continues.
I couldn't agree more, 2015 is definitely a work in progress.
However this issue has less to do with CC 2015. I've done similar tests with AE 2014 and ME 2014 to the same end.
It's a very bizarre discrepancy between platforms that I'm trying to wrap my head around. I would hope it is a configuration issue that I'm missing but I'd settle for an architectural issue that at least makes sense.
I'm doing a bit of both on my 2013 Mac Pro 8 core with 64gb of RAM. My feeling is both products are dog slow in the render department compared to FCPX, Resolve, Motion. And AE 2015 CC is a RAM hog which won't play well with others. I am enjoying off-loading render chores on AME so I can get back to other tasks in AE, but boy are they slow. One thing I noticed is that you have fewer choices in AME on custom settings (say PNG sequence exports) or regarding a color-managed workflow. And since AE 2015 CC, it can no longer play a QT movie at speed with audio. I have the latest upgrade which was supposed to address this, but I'm not impressed...