Nobody can tell you anything without knowing the specifics of your project like comp settings, footage and effects used, output formats, render settings and so on along with proper system information. Sorry, but just saying that it renders slower is utterly useless.
I have opened the same project on the same computer, haven't changed anything and used the same preset in Media Encoder.
But with CC 2017 it took 6 minutes longer to render.
We don't know what you used and you have to provide exact info. There's no way around that. Whatever issue you have could be specific to a single combination of circumstances and not occur otherwise, but we know squat since you haven't provided any details.
What details do you need? The project is the same, it only uses pictures and a lot of effects no actual video footage.
I export it as a ProRes 422 1080i25 (Custom preset) with Adobe Media Encoder: With the CC 2015.3 version it takes 10 minutes and with CC 2017 it takes 16 minutes. Both times I use the Mercury Playback Engine GPU Acceleration.
I using a PC with Win7 64bit with a NVIDIA GeForce GTX 780 Ti
have you maybe encoded the same project twice? because like Ae, AME encode faster if you duplicate your queue or send the exact same item again because it can access the cached render. if so, you should compare when you send a new composition (make a small change) that has not been encoded yet.
if you want to get to the bottom of this, we should try to determine where is the hold up, in Ae or in AME. you could render just in Ae in both versions and see if it's in the render stage or in the encoding stage. if the Ae renderer renders in the same speed for both, then make sure your video export settings are exactly the same in AME. if you suspect this is a bug try to isolate this problem: new project, new comp, a similar setup with effects using native layers.
if you are rendering through "Add Composition to AME" try to do this witn "Queue in AME" and see if the results are the same.
I have also ran a test setting a 5 seconds HD comp with a solid and add grain effect and sent it to AME both running on my GPU - GTX970 and used "match source - high bitrate" so same composition, same preset and the results were:
CC 2015.3 - 02:29
CC 2017 - 02:14
I have the same issue. Same projekt, same footage. on CC14 = render time 12 hours
with cc 17 Freakin 28 hours. What gives?
(projects are located ssd drives)
encoding: h264 bitrate 50mps. level 5.2 1 pass
dim: 4096x2048 4K
square pixel, progressive, 60 fps
Effects: only frame blending from 24 fps to 60. (native AE best quality)
Effects: A little bit color correction with curves.
footage: 4 clips 4K 60 mps, 24 fps.
I find this to be a major dissapointment:-(
im forced to go back to cc14, I have not figured out what the problem is. (i have simmilar problems with other projects)
Your projects and hardware are likely the kind of setup that benefits from multiprocessing (which is present in versions up to 13.2 [CC 2014's latest updates], but are not in versions 13.5+ [CC 2015 release onward]).
If I were in your position, I would work in CC 2017 for the faster interactivity and then save as version 13 and open it in CC 2014 to do the rendering.