The 10700ka on the other hand is newer, a bit faster, runs much cooler, is cheaper in this case, and is on a much more modern platform.
9900k does have the advantage of cheaper motherboards. Z390 can be had for as little as $100 anymore, whereas Z490 start at like $150. Honestly, I wouldn't use the cheapest Z series available for either chip due to high power draw for both chips.
The 10700ka isn't a half bad deal. Its what, $50 more than a 3700x and for games it is 15% faster ish, and can overclock nicely.
However, I still don't see a use for the 10700k in general. The cheaper 3700x being way better for productivity, so it shouldn't be bought for productivity. It shouldn't be bought for strictly gaming either since the much cheaper i5 10600k is nearly identical in games when overclocked.
Just tried the ka code and it doesn't work. I'm still looking at the 10700k as my machine is 95% only pushed hard while gaming. The other 5% being comp/decomp. I'm not rendering video or compiling code. Just web stuff outside of gaming. Putting up with a 10% slower machine for 95% of the time to be 30% faster for 5% of the time is stupid. I want the 8 cores since the next consoles will be 8 core and the majority of games are console based so I don't see the extra $100 as a horrible investment for the little insurance.
I considered Zen3 if/when it's actually widely available but don't want to deal with the "need a previous Ryzen to update bios to support it" BS. I don't have a Ryzen and I know absolutely no one else that does. Even Linus from LTT ran into this problem when he was building a system at home and had to run to work to get a CPU to update bios. What happened to the old motherboards that would go into a limping safe mode when it didn't recognize the CPU?