Most overclockers already have aftermarket coolers and are on Intel, so their cooler is still compatible. No need to factor in cooler costs unless you're a first time builder. FTBs are what, 10% of the market? A cooler is one of those things that can be passed from build to build for many generations (virtually unlimited with new brackets\adapters), you should just get a quality one anyway and put the "decent" one that comes with your CPU on ebay.
Userbenchmark already shows the i5-10600K beating the 3700X by 7-12% in gaming (1-4 core) with only 78 people that have checked in, none with a great overclock yet (the Ryzen has 200K people that have checked in, so max overclock is already represented). When we start seeing those 5.3-5.4Ghz overclocks I'd expect to see another 5-10%, extending the lead even more.
I'm a unique user, VR flight simulators. AMD has a VR tax proven by the VR Test Suite here on toms and all of my flight simulators (and all modern flight sims) use two cores max. They are horribly optimized and require very high end rigs on the CPU side.
For example my current rig-
i7-8086K@4.9Ghz
32Gb RAM@3.6Ghz
and 1080 founders@stock
-is held back by my CPU in X-Plane 11 VR. I have among the best 1-6 thread CPU power on the planet fueled by lots of fast ram, and my mid-range video card is asking me for something to do while it waits on them... Hell, a 6th gen Intel with a max overclock stomps all over anything AMD has even after overclocking for my use.
This new i5 is still getting beat by my 8086K, but not by much. It is basically my CPU with a soldered heat spreader, thinner die, thicker heat spreader, more current available, that has built in mitigations for much less money. When the peak overclocks roll in my CPU will probably finally lose its crown. My CPU hits 5.3Ghz so I expect this one to possibly hit 5.4Ghz with the upgrades.
Ryzen is often the better choice for old fashioned casual gaming. Intel is the choice for more serious gaming or modern VR gaming especially for those like me that are sensitive to ASW artifacts and need the full refresh rate of their VR HMD. But this CPU, with what I am seeing on Userbenchmark, is the far better choice for gaming in general vs anything Ryzen has.
Another thing to consider, your video card limitations may hide your CPU's limitations, but I'll get to upgrade my video card twice and still not worry about my CPU being a limitation. You may be looking at a platform bottleneck during your next video card upgrade. I kept my i7-920@3.8Ghz for 10 years, it took 8 years before AMD could match it. Ryzen 3700X ties my cousin's i7-6700K from 5 years ago in gaming after overclocking both.