I would go for the 10900kf, main reason, this one can hit up 5.30ghz, with right thermal paste and premium water cooler.
I could set my stock clock to 3.2ghz then let it oc automatically to 5.0ghz without it burning up.
Also this has more cores than that amd 5800x.
They perform near identically with the 5800x being a few % ahead for gaming but the 10900kf being a few % ahead in rendering. Neither is a bad choice. Just remember although the Intel cpu is cheaper it will need better cooling and a more expensive motherboard to perform properly. The 5800x will perform on a good B550 motherboard and mid range air cooler. Overall the cost difference should be negligible between them.
Actually not that easy to decide between these two CPU's. Benchmark scores are kinda mixed bag (depends on applications).. but I think, in real life usage, there isn't much difference.
So, what's left, is efficiency and price.
No doubt that AMD needs less power and will thus be way cooler at full load -means, CPU cooling solution will be more simple and cheaper. And you also have more choices in (good enough) motherboards. For example: I'm running 5900X with 60$ air cooler on 120$ motherboard -I don't think that is possible for 10900K.
CPU price... I would still choose 5800X regardless. Simply because of things I've mentioned above. 10900K should be much cheaper to convince me otherwise.
Gaming performance will probably depend far more on GPU than CPU. In fact, a 5600X or 10700K might do just as well for that purpose so either of these CPU'a can be considered unnecessary overkill for it.
So it really comes down to rendering performance. One point comes to mind: In addition to the already discussed installed cost considerations, if you go Intel you basically have nowhere to go if you ever want to improve on it. While the 5800X can be improved upon (and dramatically so) with a 5900X or even 5950X if you ever feel the need for more rendering horsepower.
Either chip will do a good job for either gaming or rendering.
For the I9-10900KF I would wait a bit for rocket lake to launch on 3/15.
The supposed 19% increase in IPC will be most beneficial for gaming.
Particularly with the usual intel 14nm boost clocks.
I would also spend a bit more for the K version with integrated graphics.
Having the integrated option allows testing without the need for a working graphics card.
For the 5800X that is also a reasonable pick.
But, it seems that the price has been jacked up and such chips are hard to find.
Past that, reading on these forums, I sense that the ryzen 5000 series and associated motherboards still have some issues to be resolved.
Intel at launch has usually been solid.
I would look towards the I7-11700K and a Z590 based motherboard.