As a recent shopper who narrowed down his choice to a Forest River motorhome I have a little information to share but I am definitely not the end all answer.
Here is what I learned:
Forester is a little higher end compared to Sunseeker and comes with more upgrades. The current included upgrades for a 2015 Forester are solid surface counter top in the galley, flush mount glass LED lights as opposed to plastic, included Memory Foam mattress (optional in the Sunseeker), soft touch padded ceiling, fiberglass running boards and 1/3 paint (look at photos of the standard paint schemes of both coaches and you'll see the difference). Also there are different color fabrics and full body paints for each line and the backsplash in the Forester appears to be a faux tile where the Sunseeker has a stainless steel looking material.
Compare this brochure for the Forester
http://www.forestriverinc.com/brochu...sterposter.pdf
to this brochure for the Sunseeker
http://www.forestriverinc.com/brochu...ekerposter.pdf
and you'll see a few of these things mentioned.