Both are important, but not dispositive. Mine-Cart Madness has plenty of “trains” and a relatively seamless dispatch, but that doesn’t stop it from being a capacity disaster.
Hollywood Drift, if it has issues, will probably mirror Hagrids. Multiple trains and efficient loading, but lowered cycle and dispatch times as a result of classic Intamin technical issues. Joe (above) is right that Hagrids is supposed to have better dispatch times to combat the trains’ lower capacity, but the ride has seldom been able to do so for a plethora of reasons.