I have grown with them both(cobs and great whit/red combos)...literally side by side. And there are things that the monos brings that no white, or combo of them have done yet. Bag appeal, flowering time, production from lower efficiency, higher terpenes and potency(*white base was higher K too though).
@cdgmoney250 AT's R2 is the best I have used.
We are talking about 10w dissipated of monos supplementing 50w of white. Even at 40%...they do very little to the system's efficiency.
EX.
50w white @~56% efficiency(28PARwatts, ) + 10w red combo @~42% efficiency(4.2PARwatts) = 32.2PARwatts/60dissipated = 53.66% efficiency
To look at it in photon form...
50White@56+10red@42% =157.4µmols
60w of white@56% =161.28µmols
~2.5% more with straight white.
With what I know from real world applications personal experience of many runs, and the book science I have studied and researched That is more than acceptable for the gains it has shown...then could actually flip the table(by a few tenths µmols, 161.9µmols) if you hit closer to 50% with the reds.
IMO we are starting to settle too easily now that hps is in the dust pretty good. Straight white is like a slightly sodium. on the big scale(does wonders for little guys though). Which is good, but unfortunately science as well as my experience says there's a tinny bit more to be squeeze out of it still. Not necessary todo so, but it's there.
Then if we want to really follow after AT, using high K white bases to hold the efficiency up while still getting most of the key ratios the same as a mid temp phosphor.