The only Mac with a price announced has a Xeon W-3223 and to get a fair comparison price for the Dell, I selected the Xeon W-2145.

That means the Mac has 8 cores, 3.50 GHz, 16.5 MB cache, 2666 MHz memory [1] while the Dell has 8 cores, 3.70 GHz, 11 MB cache, 2666 MHz memory [2].

So the Mac has slightly more cache, while the Dell has a slightly higher clock speed.

I'm not sure I understand how the availability of accelerator cards that aren't fitted in either machine is relevant to a price comparison?

[1] https://ark.intel.com/content/www/us/en/ark/products/193739/... [2] https://ark.intel.com/content/www/us/en/ark/products/126707/...