I’ve used the La Bella SP-47125 Super Polished set. They’re basically La Bella’s stainless-steel rounds that have been heavily smoothed, so they feel much closer to flats but keep more of the clarity and punch of rounds.
Tone: More focused and cleaner than typical rounds, with noticeably reduced finger noise. Not as bright as regular rounds, but definitely brighter and more articulate than flats—especially helpful for the B string.
Feel: Very smooth, almost flat-like, but still with the flexibility of rounds. Great if you want less squeak and a softer feel without losing too much top-end.
They sit nicely between standard rounds and true flats in both sound and price.