As has been said, a "war" would never happen. At least in the sense of what people are apparently envisioning. For the last 80 years, pretty much all the conflict has been internal family strife. And even that, like the Colombo war in the early 1990's, seems to be a thing of the past. Now a guy here or there may be taken out of the picture.

But, hypothetically speaking, if the Genovese and Gambino families had gone to war, how many members they had doesn't factor in the way people think. It's not like the regular army where everybody in the family can be drafted. A relatively small portion of either family would actually be involved in the conflict. I think the only benefit that would come with size is being able to better weather the inevitable law enforcement crackdown .