Do you mean the Supernova or Supernova XP? The original Supernova is a particle. The XP is more like the HRG in theory.
I have the XP and the HRG. Two totally different looks. I didn't think Lane #1 could build a backend ball until I threw the XP. It's a completely different look from any of the older gear. Very angular but that comes with a price. I don't find it terribly controllable but it will do some major tricks down the lane and if I can get it to the pocket consistently, I can put up some big numbers.
The HRG has one of the most unique hits I've seen. It stores a lot of energy for the back and I toss more messengers around with it than most anything else in my bag. It is a lot stronger than advertised. I bought it to fit under my G-Force Evolution and it actually ended up being stronger than my Evo.
The HRG still isn't what I'd call a backend monster if you're looking to go from one side of the lane to the other. It's very nice for playing direct lines when the heads are a little dry. I tend to have problems with it on the fresh, but when the lanes open up just a little, here it comes. What makes it stronger than the Evo for me is that if I happen to pull the Evo into the oil, it will skate, whereas the cover on the HRG is a bit stronger and can handle a tad more volume.
Jess