Strings are as much a personal preference as choice of bass is. You need to find a brand that best suites your playing style. I have used many brands over the past 30 years and I find the Thomastik - Infield Power Bass Series to be the best for my basses and style for growl and mwah!!! Treena
I found the Powerbass strings to be the least growly strings I've tried. I like DR's better for that, preferably Hi-Beams. Slowounds are good too. But as Treena said, it's a personal choice depending on your ears and bass. What I call growl, may not be what another calls growl.