To a point... but you don't have to be that stable to hurt someone, especially if you're armed. I mean I can see it gives you an advantage, just not sure it's the only thing to be worrying about...
Also what if both are stable?
You don't have to study martial arts to hurt someone either, but we do - not for the hurting, but you get my point, which is that we're trying to do things better.
Stability is not everything, of course, but it's so fundamental that you ignore it at your peril, I think. Everything builds from that. Like learning the alphabet.
If both are stable? Well, it's not an absolute quantity, but the more equal they are then the more other things come into play - but isn't it more interesting that way?