IMO that depends on what you mean by “get it”. If you’re talking about being able to run down to the Walmart or having UPS drop it at your door, there’s an argument to be made that an abs cure caliber may be better (at least when ordering online) as it’s more likely to be in stock as the panic buyers clear out the standard calibers like 9mm, 223, 308, etc.
If we’re taking about a compete societal breakdown like some kind of zombie movie, you’re probably more likely to find two boxes of 308 in some farmer’s kitchen drawer than you are 6.5 or 300 win mag.