Go with the 720. Cassette toilet is far superior, seating is much more comfortable than 820.
Is there a reason you are considering Cirrus? I am going through this now. 720 is my first choice but we can't find one in our budget. We also want it for winter camping. If it weren't for that I would buy a northstar, better layouts much lighter camper and cassette toilet but I really want the Alde heat to save battery.
I have a Ram 3500 and think if I buy the 820 I will have to give up towing anything except my small utility trailer. Real world weights are very heavy on the 820, go on the Cirrus truck camper facebook group and see.