Re: Not the same.
I use my Pi (400) over my i5 NUC whenever I can - the NUC turns into a hairdryer whenever you try to do anything remotely useful with it; the Pi just copes silently with all workloads.
It is about a third of the speed (with mild overclocking), but can run & run ad infinitum (also does 128 bit software floats for long(er) term ODE simulations).
The Xeon needs fan cooling . . . how last century!