This is right up my alley...
We know Paul use to use DW drums. I believe they make the best mass-produced drums period. But, there are differences between the kits they make now and what they use to make years ago. I have 2 DW kits myself. One made in the early 90's and one made 5 years ago. The older kit sounds better, I'll explain. DW did not make their own drum shells in the early days, they bought shells from a company called Keller and applied their finishes and hardware to them. The Keller shells are superior to what DW makes now even though DW uses the same materials and specs. Many of the "custom" drum builders, like what Paul is using, also buy their shells from Keller, add their own custom hardware, finishes etc. By going with a custom builder, you can design them to your exact specifications.. drum sizes, how the bearing edges are cut (which effects the sound), the type of finish, etc.
bd, you asked what improvement will this bring? Sound wise, very little. Paul may have just wanted a new "boutique" kit.
Personally, I never liked the finish Paul has on his DW's.
By the way, if you go to the site where Paul is buying his new kit from, there's 3 pictures of Paul with his DW kit. It's in the gallery section, page 4.