As I said it's personal choice. I've dealt with passive cooling failures in PC's for years, I wouldn't want to run the risk of my light failing and waiting on parts in flower or something. I've seen some pretty elaborate passive cooling options in PC's and regardless of the amount of aluminum or copper they throw on top of the chips they usually fail faster compared to something that has a .03 fan on it.
I'd rather limit risk of failure by at least putting fans on the bars.
I took the philosophy when building mine to make each cob independent of the others. They all have separate drivers and heat sinks and fans. I personally feel safer knowing that if anything fails it's an easy cheap replacement. It may have cost more initially especially the drivers, but I am pretty safe from failures I won't lose my whole light if something goes very wrong.
I didn't mean for this to tear down the guys build at all
I think it looks great. I was just offering my .02 CAD
Since we round down here and don't have pennies anymore my .02cents ain't worth shit anyways