I was having problems finding a downloadable version of the PRTB registration form, so I thought others might appreciate the link on the bottom of this page:
[broken link removed]
Putting my cynical cap on I would say there are probably no advantages and it's just another tax (€70)
Taking the cap off, the PRTB are supposed to mediate in the event of disputes between landlord and tenant/neighbour
Whether there's an advantage or not makes no difference though, because it's mandatory to register (although I suspect a lot of landlords won't bother)