The Criterion blu-ray is a huge, huge improvement over the old Sony DVD. Likely a combination of both less hiss reduction (much less!) and superior elements being used for the transfer. Everything is remarkably clear -- this is one of the better sounding tracks from the '30s I've heard.
Given that the restoration was done by Sony, I'd like to hear how Sony's blu-ray compares.
Interestingly, the iTunes download from a couple years back (it might be the new restoration now) has less NR than the Sony DVD and the Amazon Video download. It's also trounced by the new track.