NT4 Server on Raid 1 or 5?

We have a number of new servers arriving and i proposed configuring the NT4 Server OS(Domain Controller) onto a mirrored partition with a hot spare stand-by. One of my colleagues is suggesting we should just install the OS on Raid 5. My previous experiences tell me this isn't a good idea and not the norm but i'm struggling to find and documentation to back this up. As these servers are going to be Domain Controllers with DNS etc.. there is no need for large storage space or the extra redundancy provided by Raid 5, thus taking away some of the performance. I may be wrong but we can't seem to agree on this point. Any views would be appreciated.

Thanks