yes, but only choose linux if you have a guru to set it up for you. If you want a working server in 10 minutes and dont mind the unreliability and security holes, then windows is for you.

i use both

bear in mind that apache/php/mysql on linux rules the net

Does linux have the same functionality, like say active directory?

And what distro is best for servers?

You can use SAMBA for windows domain support and active directory i think. It is windows compatiible but if you dont mind about windows compatibility then you would use something like NIS/LDAP which is better.

For servers you want stability (read: long release cycle, not the 3 months or so that somethig like fedora offers).

That basically limits you to:

Debian
Red Hat / CentOS

CentOS is a free copy of redhat enterprise. You get all the updates but no support , but it is fully 100% redhat compatible so things like oracle will play nicely (they like redhat)

CentOS/ Redhat have lots of nice GUI tools but debian IMHO is more stable and faster and easier to update BUT it lacks the fancy tools. However, most servers wont have a GUI therefore it doesnt matter too much

For Servers. Linux blows Microsoft out of the window, hands down. Offering stability, security and maintainability.

Windows can be setup in 10 minutes, but as stated above, will give you numerous problems and issues.

If that were completely true, don't you think more system administrators would be willing to spend extra time getting a Linux server up and running?

Windows has top-notch support and already has claim to a large percentage of servers out there. The Microsoft name is know all around, whereas Linux is still mostly unknown.

The Earth was also once flat. Just because everyone's doing it, doesn't make it right.

From my experience, Linux has been more stable, reliable, and functional for my needs. It requires fewer restarts, shows less quirky crashes, and otherwise keeps on chugging for eye catching uptime.

linux rules in the large server farms (like 65%) but windows has like a 90% dominance in the small/medium buisness setting

windows is easy, many mcsa/mcse ppl out there who know how to work it.
linux is much harder, but it's a fire-and-forget kind of system, maintenance is minimal once it's up and running.