I would use ECC memory if I could. I used to use a TR 2920x with ECC but now I'm on a Ryzen 7950x with non-ECC. Unbuffered ECC memory is the only one supported by Ryzen, and it's slower or more expensive or both compared to the equivalent-capacity non-ECC memory. The latest Threadripper lineup supports Registered ECC, but Threadripper is overkill (cost, threads, PCIe lanes) for home users like myself.
Keep in mind that for my 5950X I had to buy Micron Rev E 16Gbit x8 due based DIMMs, rated 3200CL22, running 3600CL18.
I.e., they just don't ship with XMP presets.
The advantage of buying RAM with XMP presets is that the reseller who created the preset has tested the sticks with that overclock and binned the original chips accordingly. When you buy RAM that is only rated for the default speed (as ECC server RAM is), you have no guarantee that all sticks will overclock the same amount, so in the worst case one stick will bring all the other sticks down to its level.
I didn't want to have to deal with the non-uniform CCDs. Of course the two on a 7950x aren't uniform either due to silicon lottery (eg on mine the first CCD clocks 100MHz higher than the other on all-core load and 200MHz higher on single-core load), but that is a small difference. It would presumably be more pronounced on the 7950x3d since only one has access to the extra cache. So I would be using it "sub-optimally" if I didn't `taskset` / cgroup everything to run on one CCD or the other.
I wonder what workload needs more than eight dual-threaded cores, but has trouble if the additional cores have more cache or the RAM isn't factory-overclocked, and doesn't care about data integrity.
