Definately Kakashi. Guy may be strong but if आप think about their stregths a weaknesses kakashi's at a whole different level. Guy only can do taijutsu and has good Speed, strength and stamina. Whilst ककाशी can do Ninjutsu, Taijutsu and Genjutsu. and has good speed, intellegence, strength and hand signs. Also ककाशी has और experience. ककाशी graduated academy at 5, chunin at 6 and jounin at 13 but guy academy at 7, chunin 11 and jounin in 20s.
BTW if आप can't read what says below here;
The eternal rivalry between Maito Gai and Hatake ककाशी is legendary, and they both prophesied they would one दिन do battle. Both Jounin's of awesome power, in their confrontation entry हटाइए would be critical mind ful of this, ककाशी unleashes the power of his sharingan, to predict Gai's every move.