i use persistent disks in my environment and it works pretty well. what is nice about profile unity is that you can use floating pools and have the pool settings to either refresh or delete the virtual desktop upon logout. that way your users get a freshly imaged desktop each and everytime they log in. also in the case of disaster recovery profile unity really makes it much simplier than if you are using persistent disks. with PU all you have to do is replicate the file share that has the profiles stored have a couple connection servers setup at the DR site and you are pretty much done. with persistent disks things get much more complicated. here is a good write up on why floating pools are the way to go: