The difference is Optimization (Score 1)

The "problem" here is that Windows has a lot more optimization at the kernel level for transactions and allows almost every process the ability to run at privellaged levels. Linux (Un*x in general as well of course), on the other hand, has a much more secure design in general which prevents many of the stability problems Windows has while sacrificing some performance. This added optimization becomes a factor after about two dozen clients, but once Windows is forced to scale beyond a certain number of clients (100 or so I think), the "optimization" has an inverse effect while Un*x is able to scale with very little noticable difference. This is one of the reasons why NT is often used within firewalls for small to midsized intranet as opposed to larger networks and as web servers.