MULTICs has capability based security, VMS is stuck in the world of access control lists. (But OpenVMS 7.2 runs just fine in the virtual VAX 11/780 in my smartphone)
MCP's Architecture struck me as absolutely amazing and fascinating when i read about it.
Bull released a MCP VM demo development kit, I tried really hard to set it up and write some simple ALGOL for it.
If anything it thought me to appreciate how MULTICS/UNIX (and aside the pdp10 world) gave us line oriented developer-focused interactive environments that don't make ones eyes bleed.
It's no coincidence the villain in Tron is called MCP. As a former colleague who managed an A-series mainframe, MCP is actually very user-friendly. It's just that it's extremely picky about its users.