difference between old prov1x and new

what is the difference between the old prov1x and the 2013 release?

Besides the $8 a dozen (based on street sales of the old one for $40/box)?   The copy under golf balls remarkably mirrors the comments from the testers posted here over the last 5 months.  Particularly the cover durability.  Definitely an improvement.

seems like the 2013 X flys a little lower off the driver, feels softer, and is more durable...have to do some more testing but the new x doesn't seem to bite as well around the greens.

The cover durability is better and there is a new side stamp. They are very nice, I can't wait to try them.