Kinda unfair to not let me use the biggest example (DAC/user separation) just because there might be sensitive data with user permissions when we're talking about arbitrary code execution. Even still, such a concept makes privilege execution orders of magnitude harder on * nix systems.

POSIX philosophy also prevents the "keys to the kingdom" kind of exploits you can get in windows, many linux exploits are much harder to chain together simply due to this.

The * nix networking stack has always been much more mature and robust than the windows stack, although I'll admit that's not necessarily inherent to the design.