I used to use nothing but flats. Then, in 1969, I heard a stack knob Jazz bass with Rotosounds.. they were new to America then. I was stunned. After that, I began using nothing but rounds with an occasional foray with flats, like my new '73 Precision bass... which eventually got rounds. I got my Carl Thompson in 1976, and used his brand (made for him by D'Addario) of nickel heavy gauge for years. Now, 55 years after beginning bass, I am solidly in the flat wound area of things. I have several modern fives that are my builds- see my Avatar - strung with rounds. They'll stay like that. I have two five string Sire V7's (J-bass) and one has a new set of Ernie Ball Slinky flats. These are, by far, the most round wound sounding flat in the long history of flats I've tried. And I've tried almost all of them. Yes, including the Thomastiks. I'm about to remove the factory rounds from my newest Sire and install a set of the EB's. Almost all the 'zing' without the nasty upper harmonic rattle and sizzle. They also have a better feel, a better fundamental, and a punch only a flat can give you. The majority of my instruments wear flats now.