Agreed, some are better than others however in my opinion…..and I mean my opinion, the best corrosion inhibitor is CAMGUARD and according to its maker best used with either the straight Shell/Phillips/Castrols or if you want to use a multigrade, the Phillips 20W-50.
Apparently it does not play as nicely with the Shell 15-50, not that it will kill your engine.
I think you missed the humour, whether you use Phillips 100 or Shell 100….its awash. The 100 Plus would be better than the non plus.
I think none are bad, some are a bit better, depending on your requirements. And when it comes to the engines that need 120 grade the choices change a lot.