The Big Country & Big Horns are built on the same line & by the same people. I've heard it said by some folks in the know that the Big Horn is the big brother/cousin of the Big Country. The Big Horn just is a little nicer & some "better" stuff in it. As far as the AC, I'm no expert, but does any 5er come stock from the factory with 2 AC units? I know some of the dealers will order some with the 2nd AC. Also, if the person who is having problems with 1 AC not keeping the rig cool, if he would get on the Heartland Owner's Forum, and do a search, there is a "fix" that one of the members came up with, with directions & photos. It's supposed to work pretty good & be easy to do. We currently have a 30' 2010 Elk Ridge, and are discussing the possibility of up grading. From our experience with Heartland, we WILL buy another Heartland product, probably a Big Country or Big Horn.
Before I went out & bought a new tank, I'd check to find out for sure where it is leaking. We were having problems with ours leaking, first it was leaking at the cap, the valve at the tank was leaking & filling up the pipe between there & the cap. Took about 3 times for the dealer to fix that. It worked just fine until summer before this last, I started having problems again, come to find out the round part from when the manufacturer drilled the hole in the tank was still in the tank & wouldn't let the valve close. Had the problem a few more times & "thought" I'd have it fixed & after a while it would start leaking again. Finally at a rally this past summer when it started leaking again, I was frantic. The problem was that the seal in the valve was getting messed up when the valve was reinstalled because it's a tight space in there & hard to line up correctly. I bought a rubber sleeve made to slip over the sewer pipe, cut out about 3/4" of the pipe, installed the valve with a new gasket & installed the rubber sleeve. So far I haven't had a leak, so I'm "assuming" I finally got it fixed.