My favorite countertop material is "cultured marble." For bathrooms to wears better than any other material we've ever had--- including granite (hate it in bathrooms, I feel like Wilma Flintstone brushing my teeth); white Corian (stained badly over three years under normal use); and tile (grout lines on horizontal surfaces, major upkeep). We recently replaced two cultured marble bathroom counters with.... Cultured marble! There is a factory near us that does custom installations in every color and pattern imaginable. The only reason we replaced them is that they were the white with silver swirly thingies that look very dated.
The lady at the fabricator said many people with Carrara marble tile shower floors are coming in for custom light gray shower pans to replace the marble tile that just doesn't hold up under constant use. Their light gray color blends with the marble and is easy to maintain. I know two designers in iur area who are skipping the tile failing step and just installing the cultured marble pans initially.
And for the record, I think a shower/ tub combination is the most cost and space effective configuration for most bathrooms. We have four of them! Our master has a separate shower and tub--- the latter is so large it takes all the hot water from the heater for that end of the house.
If a quality material is one that lasts a long time and looks good over the life if the item and functions the way it was designed, then I do not understand why there isn't a universal embrace of high quality fiberglass tub / shower combos. They're easy to clean, never leak and the one we have looks so good I would to dream of changing it out. I think the separate tub / shower / tile matrix is, basically, planned obsolescence.
Q