There are more failures of vinyl pans simply because that material is used more often than copper and lot of people install them should have no business doing so.

Metalwork, especially pans is a more specialized trade, and the few guys that will do a copper pan will be more skilled and take more pride in their work than a vinyl layer. This helps insure against poor workmanship and failure.

Where are you located, copper pans are not used many places.

All of this said, neither is the best soultion. The best design is a topical membrane applied over everything with a bonded flange drain. This system ensures waterproofness and doesn't allow any water into the pan to fail. There is no pan.

There are two types of this system, a fabric membrane like Kerdi, or Nobleseal, and a liquid applied membrane like HydroBan or Redguard. All of those products have a bonded flange drain for their system except Redguard. You'd need to use one from the other companies.

Do a search on Kerdi , you'll find volumes on the system and product.

Copper? COPPER?(or tin) I thought that went out in the 20's! Rubber/vinyl replaced THAT in the 40's.

Surface-Applied Membranes (SAM's) are cutting edge today. I do ONLY Kerdi Showers as I can guarantee them for life, I guess "Hand Cranked" cars don't need batteries....but I far prefer a "Key Start..."

Saw them use a copper pan on this old house. Must be real old school.