If you want to be able to chamber pretty much all factory ammo, use gauges.

If you want to fit YOUR brass sized in YOUR dies to YOUR barrel for the longest brass life and best potential accuracy, use a handful of full length sized cases to set your headspace, not a gauge.

I only have ONE gun that I want to be able to chamber factory ammo in and on that one I used gauges. On ALL my other Savages I use cases for setting headspace.