That might depend on the preferences in your locale. If there is a lot of deer hunting in your area, there might be a good stock of .308 in your local stores. Of course, there might be a lot of folks with hungry .308 rifles too. If you live in an area where there's a lot of varmint hunting then the converse might be true.In our ever-changing world outlook/economy, which ammo will be the easiest to come by, 223 because everybody keeps the demand up, (but will it stay readily available?),
... or 308 because everybody else is shooting 223 and there are fewer people seeking to acquire the 308 production?