I'm on the fence with regard to quantity over quality. Both have their place. Having a lot of russian (brown/golden bear?) .223/5.56 is good to send volumes downrange. It's loud, and while not accurate in my weapon, it serves a purpose. I have a mix of stuff that fires very well and stuff that fires, uh, well...just fires.
I think the key on ammo stockpiling is: 10,000 rounds is 5,000 rounds, and 5,000 rounds is 0 rounds. Just assume things get bad for YEARS. I want all the ammo I can get. Ten rounds per day, per gun might be a decent guide.