Do you think I will notice a difference between my 2.3GHz 15" Late 2013 MacBook Pro?
That's what I upgraded from too. To be honest, the difference is not night and day, but After Effects will for sure see a bit of a benefit with the much beefier GPU. Adobe's CC 2017 apps are not nearly optimized for the hardware like, say, FCPX is - but I expect them to make improvements here soon. If you're looking to upgrade for raw performance gains, this isn't quite the big jump people expect for the cost, but it's pretty much the state of the art from Intel and AMD unless you're down to carry a larger, heavier, and clunkier Windows-only notebook with a GTX 1060 or higher.
The 2.9ghz Skylake CPU is roughly on par with the Late 2013 15" 2.3ghz CPU in terms of raw performance. Maybe 8-10% better at most. Where it shines is under sustained loads, it can maintain full speed for a lot longer before throttling to maintain the thermal envelope. So longer exports, renders, and RAM previews will work more consistently, and aided by the better GPU there should be a decent boost in export times and timeline performance. The GPU is the killer app, and since gains are much smaller nowadays between chip generations, I think that it is more important than ever to get the best possible specs. Since I bought it over the holidays, I haven't been able to truly stress the machine with PP/AE as much as I usually do, so its hard to definitively say. I'm getting back into the swing of it now though.
All that said, I really am enjoying the complete package of the new machine. I love the new keyboard, huge trackpad, more contrasty and colorful display, 3000MB/sec SSD, insane build quality and possibility of for power/4K output/data in one cable - all things that pushed me over the edge to keep it.
