Though it would be extremely unlikely, both practically and historically speaking, a smaller family like the Sopranos/DeCavalcantes could go theoretically go to war with a NY family.

I don't think the total membership thing plays into it as much as people think. A NY family like the Lupertazzi's may have 200 members. But it's not like the Army where everybody can be drafted or called into service. So it's really not a 200 vs. 40-50 thing.

And hurting the smaller family economically would probably be a more effective and practical weapon than killing guys.