Yes, it would be worse with the 7940X than with the 8700K because renders from AE, in its present form, still scales very poorly with more than eight threads.
I found that out by doing a sample render with cDNG, using a borrowed desktop PC with 8 cores and 16 threads, and discovered that half of the PC's virtual cores went completely unused (0% utilization) during that render. This just goes to show how poorly the current version of AE is multithreaded.
What's more, with only four cores getting any load, the i9-7940X only runs at 4.1 GHz - noticeably lower than the 4.4 GHz that the i7-8700K runs at under the same conditions. Plus, the Skylake architecture is a tad less efficient than the Coffee Lake architecture.
Note that this is with standard projects, without using Cinema4D (C4D) at all. If on the other hand your projects incorporate the use of C4D, then yes, that portion of AE is well multithreaded. Thus, for AE, the 7940X is worth it only if you're going to use C4D extensively.