I think that the thicker the skin, the more durable, even if insulated and relatively lighter. If you think back to your old BBQ's that you bought from the hardware store, most of them began faltering after a year or two regardless of how clean you keep it and how many times you cover it.
I've never built one of these, but I would probably go bigger just for longevity. JMHO.
My 14 gauge skinned gravity feed smoker is about 50" tall NOT including the 8" wheels and their 4" mounts. While I can move it. It takes a monumental effort to push over the 1/4" lip on my garage door apron to the garage floor. I typically need to rock it a few times like a car stuck in mud or snow. It is VERY heavy.
I have decided that I am going to build the smaller version of this great cooker. I have little choice . It seems like I am getting older every day? Not sure what factor this plays in your build but you did mention weight. IT IS however, a TERRIFIC and efficient smoker.
Make no mistake, there ain't no powder in this Puff ! And... I'm not really a crazy person but I play one in real life
The centerfeed I recently finished is 10 gauge inner with 1in. 2000 degree insulation and outer skin is .020 aluminum. Very happy with performance. The insulation keeps the outer skin safe from extreme temps, I can hold hand on outerskin when inner is at 270. Everything below cookchamber is 1/4in. Not insulated but shielded..... jmt