Win2K Raid 1 or Raid 5

We are getting ready to purchase two new servers for our network, and upgrade our NT 4.0 servers to Windows 2000 Server. For our two domain controllers, we are leaning towards deploying Raid 1 instead of Raid 5. However, I am not as familiar with Win2000 Server and wanted to know if there would be any advantages to using Raid5 than Raid 1 (besides the obvious backup advantages). For example, are there any features that Win2k offers that can only be used if you use more than two disks with Raid1?

Thanks,
Dan