Offensive.
I usually just rush and beat up the character, but I don't mash the buttons, I spam 2-3 special moves though and I rarely block so I always get owned when bosses do a full combo/finishing move.
I only mash the buttons when I'm in panic mode, like both player and opponent have 1 hit left and the round is set to the last and you must win.
I must add, while I like fighting games, I'm not a hardcore player that can memorize a full combo/air juggle and a handful of special moves.