Difference of bottom bracket cup materials: resin, plastic, metal
You have the pros and cons pretty much down. I'll add a couple:


Metal cups are stiffer.
Plastic/resin cups are less expensive.


I am not familiar with resin, but I would suppose it has similar characteristics to plastic.

From what I've seen, all the higher-end bbs use metal. Probably meaning that the only reason plastic is used is to reduce costs.

As a competent mechanic who has changed many bbs, I would favor metal. I'm not worried about cross-threading, and greasing the threads removes the potential for corrosion.