OP here.
Thanks to everyone for your input.
I was looking for a scientific discussion, and I did get it.
To clarify: I like both "traditional" *and * "modern" flats, for different basses and different musical environments, so I'm not "looking for brighter flats."
To move on to my practical needs: I guess what I'm seeking -- to add to my pallette -- are "dark chocolate", thumpy strings which yet have clear E string notes, and which retain that quality for years. No floppy strings-- I like them to fight back. Thanks to your help, I'll try GHS Precision Flats in a lighter gauge.