I'd say that Itachi or Kakashi made the best use of their 3T; Itachi could defeat most opponents with 3T Sharingan Genjutsu, without resorting to his MS, and Kakashi built a name for himself by using his 3T to copy techniques.
Sasuke/Madara made solid use of their 3T for Genjutsu or to read enemy attacks, but do not specialize in Genjutsu or copying. All of the Uchiha mentioned are capable of using their Sharingan to see chakra.
Itachi probably makes the best overall use of his 3T; he can't rely on his MS for every situation, since it heavily taxes his stamina and will go blind more quickly with overuse. Kakashi is in much the same situation, using Kamui only as a last resort or finishing move. Sasuke/Madara have the EMS/Rinnegan, and therefore don't need to hold back and make heavy use of the 3T.