Thank you.
It seems more analysis is needed before a definite conclusion is drawn.
I can't figure out exactly how many points of damage a Fighter can expect to negate by downgrading from Greatsword to Longsword...
...and I don't know if you can expect to simply haul out a new shield each time a new combat breaks out (and the old one got ruined).
I can only say that if a high-level character does four attacks, say, the damage differential you're giving up is at least 16 points, and do you would expect a corresponding +3 shield to negate maybe half that, or 8 points from every incoming attack.
On average! (If the shield can break mid-fight, it obviously must be rated at a higher DR)
Since high-level PF2 fighters very likely can increase DPS much higher than that, this 8 DR number is likely very very low.
Maybe magic shields add twice its "plus" in added DR, or something...?
If you expect the choice between shield and not shield is meant to remain an interesting one at these lofty heights, that is.
PS. Obviously magic shield can't break beyond repair like mundane shields in a game where magic swords never break, or we're back at Captain Obvious territory. [emoji854]