Just talking about Charizard, Air Slash/Overheat does the most damage among the combinations for its movesets since it's both super effective and STAB. More than makes up for the 0.1s.
Against a Machamp boss, damage-wise you have better options like Alakazam, Espeon and a ES/PS Exeggutor which overall does more damage, however, Charizard does have more HP than Alakazam and Espeon (2 highest psychic attackers) so really depends but some damage is most important in raids unless you have a large number of people fighting, you will want to go for the psychic attackers.