Do lighter strings, like .40-.95, have more growl than heavier strings?
Yes, because there is less tension to bring out the amount of harmonic overtones you get from thicker strings.
No, since you're more likely to get some fret buzz which some people like to incorporate into their playing. You get growl in another sense when digging in.
Do lighter strings, like .40-.95, have more growl than heavier strings?
Yes. Despite what other members may say...growl does have to do with string interaction with the frets and the board relative to how hard you "dig-in" to your playing effort. Light strings are more easily motivated to this over heavier strings. Your EQ setting and how you attack the strings with your plucking hand is important, too. There is a fine line between "growl" and "fret/board buzz". It is a delicate balance between the latter and how it is brought into the mix whether club or arena.
Light Strings and Growl 
