Another advantage there was that I would not have to build another computer to use two cheaper processors. But that only works as I don't think I am limited by any other factors like memory or disk bandwidth.
I did however limit the processor to a 65W TDP to reduce heat output and power usage, which only slowed down my very parallel programs about 10%, and didn't affect less parallel programs at all. (The duplicated other components of two machines would also draw more power, though perhaps not that much in comparison to processors here.)
[1] For a fuzzer you could easily give separate machines multiple random seeds, so really that is no issue. But for model checking/exhaustive search there needs to be a proper form of work distribution. I haven't a clue what the network bandwidth requirement of e.g. TLC, so that might also require faster NICs than one gets on motherboards to not stall processors on the network.