One site says the EG18 puts out 60, 000 cuFt, and another says 32, 000. Cant find any rating on EG's website either... pls
If it was the 60K, I would definitely grab some of the black ones since they would be comparable to the battlefield grenades.
People using smoke in airsoft is a really funny thing to watch. They seem to think that using 1 or 2 of those really small 20K cuft grenades is more then enough to cover up any movements they make, and they start moving as soon as they go off or shortly after.
Most of the times that I have seen them used is when a hidden squad wants to move from cover to cover. All they have done is give away their position, and not use nearly enough smoke to disguise their numbers or direction of movement.
Its more of an LCF thing in airsoft I guess :P