I've assembled my new rig this summer so I can provide "fresh" feedback on a choice.
First of all keep in mind that the choice should be based on your expected use case: what is good for me o other may not be the best for you.
i14900k has the highest single core clock but from some reviews I've seen the mix of P-core and E-core in some user case cause some problem with process assigned to the wrong core-type with the consequences of loosing performance. In addition, but this is sorta of a personal taste, Intel require you an extra tax to be able to overclock your CPU and have the tendency to dump the socket at every generation refresh.
7950x3d is the best AMC cpu... on paper and it actually is on normal multi-treading application... on the other hand when used for gaming that CPU shows some issue.
AMD is using a ciplet configuration and this CPU is composed by 2 ciplet: one with the associated 3D v-cache, and one without it.
Keep in mind that these are almost 6 month old reference and you should search for more fresh data, but for the benchmark I've looked for when used with application that take advantage of the v-cache thare are issue assigning process to the correct ciplet with a significant drop in performance and bringing the 7950x3D to a performance level of a 7800x3D a significant less expensive CPU.
For my build I've opted for the less expensive 7800x3D.
Some of consideration on AMD CPU based on my experience.
First I've notice that after installing the Ryzen master application and setted to the auto-overclock fan ramp up less, meaning there is a better thermal/power use while I haven't notice any performance drop.
Second consideration is that AMD CPU are design to bump up performance until they reach 70-80° so either a good AIO or a beefy air cooler is needed (and there is none in the 7800x3D box.
Finally AMD CPU allow you more freedom on the motherboard platform you'll like to use: you can opt for a DDR4 -base MB and save some cash or got for a DDR5 one and, according to ADM statement, have the chance to use the same system event with the future CPU family since it should retain the same socket, basically halving the setup price.