To be quite fair, I'd say MAG would move the most consoles, however, not by many at all, the reason being that Mass Effect 2 is a sequel, meaning people will already have an X360/PC for the first one, whereas new people wouldn't buy a new console for a sequel when they know nothing of the story beforehand, unless they're willing to buy the prequel (Could happen, look at Uncharted 2)
MAG on the other hand, is a new IP, made by a pretty well known company (Zipper), and people tend to rave more about first party games, especially on the PS3, as they seem to always bring something new to the table, in this case, 256 players in a match, which is something that quite a few people would want to get into. I also think the advertisements for MAG seem... better, this is just me though, as I love the US PS3 advertisements, they're tons better than here in EU, and since the FPS/Shooter genre applies more in the US, it'd be able to move more consoles.
However, this is all my opinion, I mean, anything could happen, so we'll have to see just how many consoles are moved.