The Jazz Rounds are interesting and have a unique sound, but for me they are so close to the sound of the Jazz Flats, that I wouldn't bother switching to those if I was looking for a different sound. Also, the tension on the JRs is so low that I find it awkward switching back & forth to more conventional strings. The Infled Superalloys sound and feel much more like a conventional string.
I use Jazz Flats on a Jazz bass for - wait for it - jazz, or whenever I want that thumpy sound. I use the Infeld Superalloys on a Roscoe for rock, funk, or whenever I want a bright, crisp sound.