The two are pretty close to the same size. SMG has maybe an inch of height on Alyssa, and the two are pretty much the same weight. I don't see either with an advantage there. Sarah is about five years younger, not a huge difference but a moderate advantage to Sarah. The most pronounced deciding factor that I see is that Sarah has studied Tae Kwon Do for years, whereas there's no evidence that Alyssa has any IRL fighting experience. She's clearly in pretty good shape, but the difference between aerobics and martial arts training is a big one, and for that reason I see SMG winning a real-life fight.
Of course, if you're going to take fantasy backgrounds into account, you can make up whatever scenario you want and make either woman the favorite, but that sort of negates the purpose for a poll IMO. If that's the plan, just make up whatever storyline you want and go with it.
Anyway, bottom line is that I think Sarah would win this one.
-JM