I had thought the speed difference would be more like 10-15% from all the benchmarks and tests i'd seen online. But here are the results from my own testing. Direct comparison intel CPU i7 7740x vs i9 9900KF render times.
The scene used was 3.4k anamorphic, containing lots of masking, keying, depth of field effects, distortion workflow, and LOG/LIN workflow. So very processor heavy.
7740x 4 core render time: 8:30 minutes:seconds
VS
9900KF x 8 core render time: 5:58 minutes:seconds
About a 30-35% speed increase!
Worth noting that with ONLY the after effects project file on an NAS (none of the project assets) over a gigabit network the speed went up slightly on the 9900KF to 6:30