I disagree, speaking as someone who has in fact had a weeks long job running on my desktop before. I mean if you have a fast PC (desktop processors are often faster per core, at the expense of fewer cores)
Well you have to differentiate whether your talking about an intel desktop machine or a "workstation" class machine. The difference at this point is the "workstation" is using xeon class processors, and has ECC. The problem is that the "workstation" has exactly the same processors as the rack mount machine running in the server room with a much better power and cooling environment.
That said, it is possible to get something like the Xeon E5-2637 v3 which is a quad core, 3.5 Ghz (+turbo) CPU. Sure its not the the 4+Ghz you can get on a "desktop" CPU but it does have a LGA 2011v3 which will give you significantly more memory bandwidth and ECC.
Frankly, while I think running anything besides a desktop workload on a "desktop" is silly because those kinds of workloads tend to be better handed with servers. It does seem that intel has lost its way a little when it comes to extreme single threaded performance. Particularly in the server space. Why they don't offer a 200+ watt pig clocked a few percent higher seems strange. Pretty much everyone else does it (POWER8, z13 (@ 5.2 Ghz), AMD, etc).