Thanks Allthat
The red in the RGB laser in my avatar has a 660nm at almost 400mW, and the RGY on the left has a 115mW 635nm in it. They looked very similar in brightness with a reasonable amount of haze in the room, but when I really fogged it up, the 660nm seemed to cut through it better than the 635nm.
It's a tighter beam on the 660nm, but the additional power must also help it to punch it's way through.