Longevity depends on maintenence and avoiding any water leaks. The laminated walls can delaminate if any water penetrates the seal. On the other hand, if water gets behind the aluminum siding, damage will occur. Repairs can be easier with aluminum siding. Our first trailer (Sunline) had aluminum siding and was a really great trailer. Our Minnie has laminated walls. I really like the laminated walls for ease of cleaning and waxing. Another factor is exposure to UV rays. Laminated walls can get dull and worn looking if not maintained and exposed to a lot of harsh sun, which is also hard on all the roof seams. Since you are in SC, longevity will depend on how the unit is taken care of, and how it is stored. If indoor storage is an option, it will really make a big difference. I'm lucky to have affordable inside storage all year for my Minnie and it really helps with maintaining roof seams and preventing UV damage.
Bottom line, I'd go with the unit with the best overall quality, looking especially at fit and finish. Depending on what layout you are looking for, I'd also suggest looking at Winnebago trailers. Since we've had ours (fall of '13), I've followed as many forum posts as possible, both here and elsewhere, and owners of Winnebago trailers have been very pleased. But, as with just about every manufacturer, there have been a few negatives reported, but most issues have been minor.
But, I will tell you that we owned 3 Starcraft popups, and they were very nice trailers. We had major issues with one trailer, and Starcraft took care of the problems without any hassle. If you are looking at Starcraft trailers, consider their sister company Jayco. Jayco makes some pretty good trailers although I didn't like some of the things they were doing with their lightweight trailers when we were looking to replace the Sunline. As you look at trailers, compare the length of the awning as on some of the Jayco trailers, they were installing shorter awnings (by a couple of feet or so) than they had to. I like to have as much awning as possible.
Good luck in your search!
