He seems more comfortable with the old stuff... like he's been playing that songs for years, it's completely logical... on the other side, the new songs are new, and some of them quite difficult songs to sing, specially if you don't rehearse on a daily basis (Ashba needs to play the songs more often, like the solos of This I Love and stuff). Axl seems, right, out of breath, which makes sense because he's been out of stage for 2 years and now, all of a sudden, he plays four shows in a week or so and two of them are 3 and a half hours long.
It's like, it's totally an Axl thing: crazy, amazing stuff, lots of drama and things that don't seem to be as right as they could be. It's Axl's life.