The Sunseeker and Forester are produced on the same assembly line using mostly the same components. The Forester is marketed as more upscale. The best comparison I can give you is to think Chevy versus Buick or Ford versus Mercury. Same basic products just a bit more bling in the upscale versions.
You can download the Forester brochure
Here. The Sunseeker brochure is
Here. Download them and compare and you'll see there isn't a lot of difference. The available options, shown in the brochure, on a Sunseeker can make it very comparable to a Forester but it won't have some of the bling features. Both brands have fiberglass roofs...
We chose to buy a Sunseeker as that is the line the dealer I wanted to use carries. Having the right dealer was more important to me than some trim differences...