My "go to" strings of late are La Bella RX Stainless rounds. They last, sound good, and feel better to my fingers than most other stainless rounds. That said, my all-time favorite bass strings were the old D'Addario XL Reds back in the late 80/early 90's. The outer windings were copper or copper-coated. They were laser-bright for the first couple weeks and then mellowed nicely. The copper would develop a patina that would turn your fingers and frets green like cheap jewelry, but as they aged, the strings got a very flat-wound dark woody tone.