Originally Posted by
Kontact
Plastic cups work fine if you aren't a klutz with tools. Trying to replace a plastic cup with a metal one might create issues.
In my Ti MTB I've had a cheap BB with two plastic cups for a couple decades. Completely proof against galvanic corrosion.
I'll add that I've seen quite a few LH plastic BB retaining cups/rings that are/were cracked and the BB and bike worked just fine. Including one of my own that saw many thousands of miles after the install (when the crack happened...) If the BB was otherwise well installed and the cups stay tight the crack is likely to be a "no big deal", till it's removed.
Generally, I much prefer metal to plastic for fittings (and frames but that's another topic). But there are some applications of plastic in bikes that work quite well. Andy