Which tail type is better in order to obtain higher speed?
Lose the tail.
By Staff Sgt. Bennie J. Davis III [Public domain], via Wikimedia Commons

Split brake-rudders will do the trick.

You can also try and beat NASA and Boeing to the Active Flow Control tails.

Or just settle for a T-tail.



The horizontal tail plate effectively increases the aspect ratio of the fin by virtue of the 'end plate' effect. The T-tail configuration is especially popular on gliders.

(Flight 1977—PDF) Early Boeing 757/767 designs featured T-tails to reduce drag.