Car is still a pretty deadly weapon, so is a plane, bigger car and a bigger crowd things could have been much worse. The Nice attack didn't involve a gun or bomb and managed to kill 86 people and injure 434.
Contrast that with the heavily armed San Bernadino attackers who killed 14 and wounded 22.
I don't think there is ever a correlation on the method. The degrees of carnage always vary depending on all factors of the attack.
it just needs to stop, reading some of the things this asshole was involved in and said I have no clue how the hell he was walking around London. wtf?