You can benchmark Apache, IIS and other web server with apache benchmarking tool called ab.

To benchmark a web server the time it takes to serve a page is not important: you don’t care if a user can have his page in 0.1 ms or in 0.05 ms as nobody can have such delays on the Internet.

What is important is the average time it will take when you have a maximum number of users on your site simultaneously. Another important thing is how much more time it will take when there are twice as many users: a server that take 2 times more for 2 times more users is better than another that take 4 times more for the same number of users.