I saw both bands numerous times in the 80's. DiMartini is a hell of a guitar player and vastly underrated when the topic of "best guitarists" comes up, especially from that era. Ratt always put on a great show, especially with that classic lineup from the 80's.
Dokken, well, anyone who knows me knows that I am a huge fan, especially their stuff from the 80's. In my opinion, they are another band that never quite got the recognition that they deserved. George Lynch is one of the greatest guitar players of all time in my honest opinion.
As much as I like Ratt, Dokken beats them on pretty much every level, other than possibly stage presence.
Vocals: Don crushes Percy
Guitar: Lynch is better than Warren and definitely better than Crosby.
Bass: Probably a tossup in bass playing, but Pilson's background vocals get him the nod here. Interestingly enough Juan Crocier was the original bassist with Dokken when they got their first record deal and is the bassist on their first major release, Breaking the Chains. He had been playing in both bands but decided to go fulltime with Ratt and Jeff Pilson replaced him.
Drums: Mick Brown crushes Blotzer. Bobby is a decent rock drummer, but Mick Brown is definitely the better drummer. Again, he also has the background vocals to go with his drumming which helps him beat out Blotzer.