Most of the reasons to play (and pay) on Blizz servers are gone.
Superior stability?
Balance?
Communication from devs?
QoL changes?
Game Masters who can help/exist?
Refunds?
I think Blizz loses to p-servers on all but refunds, they tie in that category.
Oh and Blizz has more lawyers, one even worked his way to be head of WoW.