Hi Drakeredcrest
To be fair the Xserve was discontinued in 2011 and is still supported by OS X though how long that will last is another matter.
The advantage of an xserve over a mac pro is redundancy, hot swappable parts and IPMI (lights out management).. They are a lot noisier than a mac pro and have less expansion slots. You'd also need a rack ideally as they'll pick up a lot of dust if left on the floor.
You can still run current storage arrays (fibre/sas) with them but not Thunderbolt ones (same goes for the older tower Mac Pro's)
If you can get one cheap they're great for a lot of things but really you can make yourself a far more impressive Mac Pro or make a decent server from a Mac Mini with a thunderbolt chassis. What are you hoping to achieve with your setup?
Thanks
Beatle