I would not say Parasound is much better if any then Rotel anything. They both make quality gear on all levels but to say that it's much better I simply don't agree.
I have Installed countless Rotel and Parasound amps , pre's ,receivers , 2 channel , theater systems , Tuners which I have always found quality in both companies.
Unless you can listen to both said amps you wish to consider or all gear of those brands for that matter with the speakers you want to power , then there is no clear choice here.
On a side note Rotel everything can handle 4 ohm loads with ease. Even their 75 watt receivers and 50 watt amps. Same goes for Parasound , no concern with 4 ohm loads. Only concern would be how much power will be required to power unsaid speakers in unsaid room.