The only pin I own that has a protector installed is the one I gifted my mom, she is in Germany, half a globe away.
There is no way I can teach her how to remove the glass and clean/wax/new balls.
Hence the protector, I rather have her grind that one into pieces with worn balls and grim all over than the clear.
But otherwise I would not ever consider it. I listen to all of Chris' (Ks) podcasts, why he had Chris from Cointaker install a protector on his BM66CE is beyond me.
I own two Iron Man, one with mom, one here in my collection.
Hence I believe I am in a good position to compare the two playfields head to head.
My opinion: stay away - unless you are mom and do not know how to maintain a decent playfield and replace balls every now and then.
Its like sex with a condom.....and please, your "your mom" jokes I do not need to hear now...I know I set myself up for them, hahaha.....