Love La Bellas for the old-school thing, but that's not the sound I'm after.
Love DR Legend flats except the E string has that vintage "clunk" factor, which again isn't what I'm going for.
Wanted to love D'Addario Chromes but I found the texture to them tacky/sticky, not a pleasure to play.
So far of what I've tried, I've loved the Fenders best, even if their tension balance within sets can be a bit wonky. They have a growl and clarity that is very pleasing in my Precision Bass. I've heard Ernie Ball Group flats aren't too dissimilar... or what about Rotosound Jazz 77s? What other flats might be in a similar ballpark?
Absolutely recommend to try Dunlop stainless steel flats - very nice strings.
I have some thomastik sets and labellas obviously but out of the bunch, the dunlops feel the most balanced between tension, sustain and solid brightness of the string.
I very much love them and especially use them on my Jazz basses.