blu,
I have the large ARB and love it. It's my second ARB. Had the mid size but sold it to get even more capacity.
Basically, ARB, Norcold and Engel are all the same (so I believe), just different color paints. Engels are sold more through RV channels and ARB through wheeling places. I think Norcold goes more through marine, but am confident they are all made by Norcold.
I'll see if I can get shed guy to come over and make a post on this topic. He's in OZ and most over there have them.
I found it surprising how much I use mine. It's used all the time.