I don't think aluminum is a guarantee. I don't know anything about the Peak brand, but there are stories for other brands of badly welded frames with broken welds. If the aren't weld correctly they break on flexing of the bed/camper.
For any brand, you need to fully inspect for leaks. Even fiberglass models like Bigfoot and Northern Lite can have leaks and they are just as much of a issue with those brands to fix. For campers, the biggest problem compared to a boat is that there are a lot more holes to potentially leak. For instance, you don't usually drill holes in the bottom of the boat except for through hulls, but there are lots of holes in the top of campers for lights, vents, etc. that are potential spots for leaks.
I prefer aluminum frames, btw. But, all types can be good.