KVM on Ubuntu Server or Xenserver - Specific Disk requirements

So I've been playing around with my N54L HP Microserver, and decided to wipe windows from it which was running as a server OS for me.

I'm debating a couple of options, with some specifics around the Virtualisation elements if I may be so bold as to ask for your knowledge....

(I need to be able to run a couple of windows VMs and a NAS type VM on top of whatever base I choose.)

I did install Xenserver, as Type 1 bare metal seemed to fit my needs. However, because the N54L doesnt support passthrough, it meant all the hard drives would be virtual drives and not native drives.

(My storage solution is to keep the Data disks seperate and mount them in the VM to use, so that if I change OS I still keep the data).

I have considered using Ubuntu as the base and installing either Xen or KVM on top to allow me to mount the drives.

Questions - will i notice much difference in speed between type 1 and the type 2 above?
am I missing a trick?
Xen or KVM?

Ideally, whatever solution I use I would need to be able to manage remotely via CLI or web interface. Ilnow Xen supports this.

Thanks