Definately Kakashi. Guy may be strong but if wewe 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 Kakashi can do Ninjutsu, Taijutsu and Genjutsu. and has good speed, intellegence, strength and hand signs. Also Kakashi has zaidi experience. Kakashi graduated academy at 5, chunin at 6 and jounin at 13 but guy academy at 7, chunin 11 and jounin in 20s.
BTW if wewe can't read what says below here;
The eternal rivalry between Maito Gai and Hatake Kakashi is legendary, and they both prophesied they would one siku do battle. Both Jounin's of awesome power, in their confrontation entry songesha would be critical mind ful of this, Kakashi unleashes the power of his sharingan, to predict Gai's every move.