There are a couple of differences between the 4* and the Sportster that I've noticed. (I own and fly both, and have maidened and trimmed a number of others.)

The 4* is lighter and won't penetrate the wind as well (it gets tossed around a little more), it also has some "down" pitch coupled to rudder inputs which make knife edge harder. The SS lands a bit faster becasue of the cleaner design (less drag), and flys a little faster with the same engine prop as a result.

The SS also looks a LOT nicer than the 4*, unless you hate the trim scheme of course.
Dennis-