Personally I would go for the most cores possible. The clock speed, even overclocked is going to top out in the upper 4ghz, maybe 5ghz range. Anything higher than that is risking instability. Anyway the marginal gain from the clock speed is to the best of knowledge, fairly small. More work will get done with more cores without the heat problems associated with higher clock speeds. Just my two cents worth.
Cheers

I have found that performance scales pretty well with clock speed. The difference is that once you get into higher clock speeds above say 4 ghz or so, power consumption starts increasing exponentially. So you're best off with a 3-4 ghz clock speed with as many cores as you can get.

Another factor that I take into account is how many machines I want to deal with. I'd rather run 2 machines vs. 4 machines even though the CPU's on those 2 machines cost quite a bit more. Less overhead overall in terms of power consumption and all the other parts needed for multiple systems.

If you budget allows, a 16c/32t Ryzen 3950x or 5950x is a good high core count CPU that also has high clock speeds. I have been very happy with mine.

Many cores and an as large Level 3 cache as possible !
Yves

At what point do you take which CPU into consideration as opposed to just speed (GHz). Let me explain.

I understand more cores and more GHz. But the performance of GHz of an I9 cannot be the same as that of an I3 at the same GHz.
The only example I have is changing a 4 core i3 CPU 540 @ 3.07GH to a 4 core i5 CPU 760 @ 2.80GH and saw more points produced.
And where do the BOINC benchmark numbers come in?

I'm looking at converting an old Phenom II X6 1055T to something else by changing the motherboard, CPU, and memory. Everything else in the tower will do.
The Ryzen 3950x and 5900x above look interesting. It can't be that the GHz of an AMD CPU is the same as the GHz of any other AMD CPU. Or is it? Then it's just cores.
Going from a Phenom II X6 to a Ryzen xxxx must be part of it.