You will find the gun will dictate how the case should be sized.

Examples: My Kimber Longmaster Classic (223 Remington), Remington 700 (221 Fireball) and Sauer 202 (7mm Remington Magnum) all have tight chambers and using the FL sizing die in accordance with the manufacturers instructions provides the correct amount of shoulder set-back, ~.002". Rounds chamber easily and my loads are very accurate.

My Ruger #1 (25-06) has a generous chamber and FL resizing the brass in accordance with the manufacturers instructions results in too much shoulder set-back, ~.006". That much resizing will dramatically shorten the life of the brass. With this gun I need to use a case comparator to get the die adjusted properly so I only move the shoulder enough to facilitate chambering.

The only guns I neck size for are my Fireball and 25-06. The Fireball case (a shortened 223) is very robust and easily handles the powder charges without excessive case expansion. I reform military 223 brass to 221 Fireball. The 25-06 does well with neck sizing for 2 or 3 firings before I have to bump the shoulder back. I also find myself annealing the 25-06 cases more than any other. I reform 30-06 to 25-06 from Greek military brass.