Are you saying that maxim has a higher suppression build up stat than Vickers?
Sir, you go too far.
It depends on the situation. Maxim ignores suppression by its own, so it will shoot and shoot... that is why it wins versus a HMG42 even if the Maxim is out of cover and HMG-crew in medium-cover.
And the stats say it so, in Stats Maxim has the higher nearby_suppression_multiplier and Suppression_multiplier. Vickers has some more amount by it own.
Vickers has some crazy burst multiplier, it is a complete broken weapon. (same with HMG42, which arrieves way too early) And Maxim become some crazy rate of fire Multiplier too...
Edit: If you put all together… Allii HMGs have stupid stats. xD