It was probably not dramatic if it was slower at all, there is a reason so many of those workstation processors died out in the 90s.
I imagine these chips might have been optimized for throughput on well-suited and carefully tuned programs, where the compilers could be convinced to put out good code (since it was apparently something like a VLIW).
Domain OS was a multiuser, multitasking OS running on a Motorola 68020 with 4 Megs of RAM with distributed filesystem and diskless clients which did swap over the network. Ah, and with versioning filesystem. And Spice simulations were resonably fast compared to a 386/40 running Pspice on MS-DOS.