I don't agree with your comparison. NT's security model does not have to be exposed to every single end-user for it to be useful. For e.g. things like taking a

I don't agree with your comparison. NT's security model does not have to be exposed to every single end-user for it to be useful. For e.g. things like taking a process token and stripping its rights to adding a layer of security to the processes is much superior to a chroot type hack. Modern UNIXs have added apparmor, but then again I was comparing NT with the OS landscape in the early 90s. Also file system ACLs is another place where NT was superior. There was nothing comparable elsewhere at the time. The problem is you're comparing two unequal things and calling it even. Linux clearly has had to deal with several challenges in improving its design due to its UNIX heritage (time-sharing OS, synchronous I/O, blocking syscalls, etc), while NT did not because it was a fresh design. Frankly this type of discussion is more suited for a comparative analysis type paper than the comments section. Also, FWIW - I don't claim any special expertise or knowledge on OS design, its simply a topic of general interest of mine.