[greengiant]

I've had both fiberglass and aluminum in my short, 5 years, of TT experience and I don't see much difference...yet. Maybe others with more knowledge can share the basic pros/cons.
I would agree that the tongue weight will be much higher on the Hideout, as well as the Gross Trailer weight. So you'll WANT to run numbers on your truck before getting a trailer of 8Klbs to make sure YOU are comfortable towing it. There are plenty of threads with towing information to educate us here so we don't get too big of a trailer for our trucks. (not saying this is, or is not, the case for you)
My hideout is very similar to what your are looking at, and after one year we really enjoyed it and had good luck with it. Changed a few small things, but overall satisfied-and it has that aluminum siding. The major difference I see is the space inside the unit. That big slide in the Hideout really opens up the floor plan compared to what I'm seeing in the Bullet (which would account for a lot of the weight difference in the two.
Good luck!