Mitch, the Sport is the slightly wider version of the 18X--22 and 3/4th" beam, rather than the 22" beam of the narrower boat. My friend ordered the Sport. He's going with the standard fiberglass layup, not the Ultra layup.
I've no GPS and have never tried timing myself in the 16X; I'm just happy to be able to outrun my usual paddling partners (when I feel like it). Subjectively it seems to crank right along when I really push it.