The One X has the better display. Maybe it's the slightly higher pixel density, thanks to the slightly smaller display (4.7 inches compared to the GSIII's 4.8 inches). Or maybe it's just that I prefer Super LCD2 to Super AMOLED HD. Regardless, I choose the One X on that spec.
I'm going to take a pass on processor and chipset for the moment. That's something that's better tested in the real world and not after a few hours of demos. But chances are we're going to see pretty good battery times on the Galaxy S III, due in part to it having a greater capacity (2100 mAh) compared to the One X (1800mAh).
I'm not crazy about the physical home button on the GSIII, but if history repeats, U.S. carriers might well opt to get rid of it when the phone hits the states. (On the other hand, it's nice to have a menu button, and multitasking by holding the home button is intuitive enough.)
If you've listened to our Galaxy S III podcast, you know that I'm not crazy about the latest version of Touchwiz. As far as home screens and the launcher go, they're functional, but they're more of the same. But Samsung's camera app, and the S Voice and motion tweaks are pretty killer. We'll call that one a wash, perhaps, because a third-party launcher will cure some what Touchwiz ails. At the end of the day, though, it doesn't feel like you're using an Ice Cream Sandwich device like it does on One X.
When it comes down to that "feels good in the hand" factor, though, the Galaxy S III wins out. It's more curvy than the One X, and it's a full 0.3 millimeters thinner. It's 3 grams heavier, though, but it's nicely balanced and doesn't feel overly hefty.
So which one would I choose? Which of my children do I prefer more than another?
Gonna sleep on it. In the meantime, enjoy the hands-on video after the break.