>>23461830He's not better at using Assault Vest, Machamp lacks Drain Punch which means absolutely no recovery. Also has worse defense and HP, meaning he fares worse against physical attackers while not faring much better against special attackers.
Dynamic Punch is hax based and unreliable, you'd want Guts on AV to act as a status absorber anyways. If you run Guts there's no reason to use Machamp though, so it's outclassed barring hax.