I've been a fan of Rotosound 66's for quite a while. However, I've found a new long-lasting stainless string that I like even better. Ernie Ball Stainless Slinky. Yep. Most recently (within the past year), I've tried Pro Steels, Roto 66's, DR Hi Beams, and the Ernies. For me, the Slinkies beat everything, and, as I mentioned, last a long time. For me, strings are pretty much dead when you slap the E string and get kind of a thub thub sound instead of brightness. The stainless Slinkies stay bright for months. The most disappointing of the above strings were the Pro Steels, which lost their sparkle fairly quickly.
. . . . I mean . . . . um . . . . I've been rather disappointed by Pro Steels on every bass I've tried. . . yeah, that's what I meant to say 