I think the new 17" should be better because of the screen. After all, it kept the ExpressCard, it still has 6MB cache, and the battery was already integrated.
I bought the 13" for audio because of portability (didn't get the 15" since there was a huge downgrade on losing the EC and that wasn't worth the money anymore). I'm running Logic Pro and getting along with the crappy res using screensets alot when an external display isn't available. I'm only recording 2 channels on a Duet while mobile with this rig so it works for me and the size is a huge plus.
There are many reasons to record at 96k but let's not go there on this thread.