Slicks will outlast in longevity, surface contact and grip..... but DOT's are relatively cheaper and can give sufficient performance abilities.
The purpose of a DOT race tire is to make a close-to stock size tire with the DOT stamp so adhere to race rules (in certain clubs/races) that enforce the DOT-only rule. Basically, they want to give the appearance to the fans that "you can buy almost this EXACT bike that these guys race on"; usually seen in Stock and SuperStock in WSBK. A new rule change for 2013 in WSBK is that teams now have to use "headlight" decals on the bikes.
The material on a DOT race is more performance engineered than a DOT street tire (which compromises performance with longevity), and they are a cheaper alternative for track/race days than slicks are. DOT race tires aren't "bad", it's just slicks are engineered "better".
Don't think the DOTs race give you any boosts in the rain either..... lol. There's a huge difference in full rains vs DOTs, which is why I decided to go full slick or full rain from this year on.
I would never run a street DOT on the track (again...), my Q2's just shredded out of nowhere once my pace picked up, so either race DOT or slicks will be reliable for track/race purposes.