I’m a recent convert to flatwounds this year after a lifetime using roundwounds, presently using the “bridge cable” 1954 Vintage 760M and the 760FS on two Fender Player precisions, and I’m waiting for 760FL and Olinto’s due in a few weeks.
I find the 1954s comfortable, playable, bendable, and I’m not a particularly good or strong player at all. They are also bright, articulate and musical without the noisy muddle of roundwounds, and much more percussive. I like them very much.
The 760FS are a little easier to play and sound a little more cutting. Can’t say I prefer them.
The 760FLs will go on a jazz bass. If they’re noticeably different from the FS I will probably prefer the FS.