Aluminium locknuts are very variable. IME the plastic of the locking device can often push its retaining aluminium wall outwards and be useless after the second time they are tightened. For anything other than 12th scale front wheels, I would avoid aluminium locknuts.
Serrated locknuts should form their own indentations in plastic wheels creating an effective 'ramp' that the nut has to overcome before it can come off. Adding in the resilience of the plastic it should perform better than a locknut until, as pointed out above, the serrations wear. Since it is easier to see that than if the plastic in a locknut is worn, the best mechanical engineering solution would be serrated faces on the wheel nuts. HTH
