Well, I think I have a new favorite string. Since La Bella discontinued the Stainless Steel series, I went back to the Rotosound RS66. I still love it, but I was very curious about SIT strings. Tried their RB (Rock Bright) Stainless and they were indeed bright, a little too bright for my tastes, possible masking some lower end tone. The feel was amazing, though. I felt I could play faster and better with them. I think they're about as stiff as the Rotosounds, but I'm able to slide string-to-string more easily, allowing me to play faster. Even if they're not as stiff as the RS66, the fact that I can more easily cross strings maybe makes them feel that way, since there's less resistance, therefore less needing to put pressure on the string to bend it. SIT also has the Power Steel strings, which don't have some sort of process that bonds the core to the wrap, which seems to make them inherently less bright. I put them on yesterday and I think the Power Steel is the best balance of everything I like in a string. Not that I need to know who uses/used their stuff if I like it, but they list Jack Bruce.
Anyway, so pretty psyched I found a string that seems to meet all my needs and feels great.