As someone in the transit bus industry, Starcraft are the cheapest of the cheap off the lot, and the corners they cut come out in longevity and in safety, I wouldn't even consider one when buying.
Fiberglass is largely used in the transit but industry for aesthetics, it can be easily molded into complicated shapes and with proper production, last a very long time. (25 year expected life span) That being said, it is more expensive to produce and repair than steel, and is not as strong structurally.
Fiberglass will crack easily with impact, so if you're going to be driving down smaller roads into back campsites, a solid whack from a tree branch could be very damaging, and once its cracked, it must be properly repaired or else it will allow water in, further degrading the fiberglass. Steel is far more durable, it can rust, but it will dent and remain strong with impact. The downside being that they look like tanks and do have a significant weight penalty.
Fiberglass is about 0.055lbs/cu-in compared to about .3lbs/cu-in for steel. At comparable strengths, steel weighs about 3x as much per unit of area.