If buying a new MB, I'd prefer 10700K.  

 
That's a good price for the i9-9900k.
 
Check out benchmarks on 9900k vs 10700k - very little in it.
 

Nereus
 
That's a good price for the i9-9900k.
 
Check out benchmarks on 9900k vs 10700k - very little in it.
 

I own a 9900K. 
 
If buying new, I'd rather have the LGA1200 socket and various features that the 10700K offers.
 
At $299 though, it absolutely smokes a 3700x.

kougar
AMD's 5000-series chips with a B550 board would be a way better buy at this point, but since they can't be easily sourced yet Intel probably gets the nod. 

I'll wait to see them in the wild. Ooooo...
 
https://www.3dmark.com/search?_ga=2.147356535.1353367224.1604681767-1584897410.1604414567#advanced?test=spy%20P&cpuId=2759&gpuId=&gpuCount=0&deviceType=ALL&memoryChannels=0&country=&scoreType=overallScore&hofMode=false&showInvalidResults=false&freeParams=&minGpuCoreClock=&maxGpuCoreClock=&minGpuMemClock=&maxGpuMemClock=&minCpuClock=&maxCpuClock=
 
Literally the same performance as a 9900K.  My 9900K does 11,700+ TS CPU with 4000CL19 32GB (dual rank).  At stock clocks with 120mm AIO.
 
https://www.3dmark.com/spy/14394730
 
5800X is $449???  LOL.
 
 

PCIE 3.0? No value for future upgrade or use.

DeafRX

vanity_lost
PCIE 3.0? No value for future upgrade or use.

Not like any newer chip with PCIE 4.0 is any better considering DDR5 is still due to be released in a year. They're all going to be in the same boat.

Lately it sounds like they're going to skip PCIe 5.0 and jump straight to PCIe 6.0 lol.
 
 

Unless you're on a budget, I'd build with the 10th gen Intel or 5000 series AMD. I think based on benchmarks I'd go 5600x if $300 is your price point for a CPU. Then you have to consider availability, can't buy any of the new hardware right now. 9900K and z390 are a dead platform, there is no upgrade path for them. I believe 11th gen intel is supposed to work in a z490 board so you have an upgrade path if you were to buy 10th gen now. On the AMD side, rumor has it the 5000 series CPUs are the last to support the AM4 so you'd be stuck there but still have a nice rig for years to come.
 
I currently have a 9900K. I play at ultra wide resolutions and there is not a huge difference in FPS, at least not to justify the cost of a new CPU and motherboard. If I were building today and parts were available, it'd be a Ryzen 5900x, x570 mobo, 32GB 3600mhz ram, RTX 3080 for me. 

Don't forget that you can buy an Intel Performance Tuning Protection Plan for Select Processors if you're interested and plan on overclocking an eligible CPU..Dirt cheap insurance for an expensive CPU