While Guy is undoubtedly stronger, Asuma is much more versatile and he can teach better, i mean obviously Lee was taught but Neji just mainly trained with Hiashi and Tenten didn't learn a bunch from Gai since she is a weapons specialist.
Gai would irritate me but I would love for Sakura to train with him, asumi would be okay, Sakura would easily surpass him though....I always asumme I'm Sakura in these situations
I'll love to train under gai he super insane and I would love to learn gates of opening train sleeping train dead train every second I would loveit then i would disappear from the village and learn the ways of madara how to hate everything
Hmm, difficult choices...I like Asuma's attitude better, but I think that Gai's pressure would do more to let you become a fine shinobi in taijutsu, so I'll go with Gai-sensei