Love their flats too and tried their Deep talking rounds, 44-110 on my Fender American standard jazz bass, It totally nails what I was looking for! A deep, clear, chrunchy sound that isn't harsch but just pure articulate, with lots of meat on every string!
After break-in they just stay that way, way darker than most steels, for a loooong time.
They sound quite similiar to DR Fat Beams, except maybe a little less slap-friendly tone and more fundamental! Also that metallic sound that most LaBella strings have, especially present in hi mids - highs.
Great strings! Really brings forth fundamentals in a clear way, altough not as soft as nickels sometimes do.
Bass is also nice to eat.