I don't know what they base their decisions on. Probably what songs they like most and which ones they can play best, I would guess. To be honest, they need some more work on St. Anger and Frantic. They just didn't sound as good as the others. Given that it IS new, though, I suppose that's to be expected somewhat. The fans, though, were WAY into them, and it seemed like we all knew the words (since everyone was singing), so to me that's a sign that it's well-liked.
The most songs they played from any of their albums was 3 (Master of Puppets and The Black Album), and the only album they didn't touch (save Garage Inc) was Load. I kind of wish they had played Hero of the Day, but I guess the slow song of the night was reserved for Nothing Else Matters (which was one of the highlights of the night, as everyone was singing, and since it's not a loud song, you could hear us more than James -- very cool stuff).