65DZUS is pretty big!
I have no personal experience with the ARB 50QT. I do have the Dometic CFX-65DZUS. It's huge! Two people 5 days would not be an issue. It actually has 3 zones, with storage above the compressor assembly being slightly warmer than fridge temp.
Just be aware, it really is big!
Part of that "big" is in depth, so "stacking strategy" is important, and having the ability to reach down into it. This is part of why I have it mounted on the passenger side rear floor.
In that last picture, the raised floor is 9" above the rear floor of the Jeep, and the fridge is sitting down on the center hump.
So while I really like having the dual zone, before buying, I'd make a cardboard box to "simulate" it sitting in the Jeep. Engel makes a nice 50Qt Dual Zone as well.
If I remember right jandymendo (member name on this forum), has the Engel 50qt dual zone, and may be a good person to PM for more info on actual usage. He's a straight shooter.
Not trying to warn you off, as I am very happy with the 65DZUS, but it does take up a lot of real estate.
Good luck with you choice! :beer: