Led setup, single led or COB?

Hi, I have a question.
Is better a purple cob led or a single led setup like marsh??
I want a good choise for a 3ftx3ft grow box, now i'm running a 9 cob led (search amstergrow on aliexp) with real usage of 400w.
A setup with single led is better?
Or a classic 400w hps perform better??

+1 Here. Looking for info on COB vs multi LED board vs the ones with both COBs and individual LEDs, and dimmable/switches for veg and bloom cycles.