I have used these strings on my fretlesses for many years, and have found something good about all of them:
GHS PRECISION FLATS: Old school thump with clear tone and smooth finish. I have them on my SX Shorty Jazz Fretless and a Carvin AC40 Fretless currently. My fav flats.
GHS TAPEWOUNDS: Something new I am trying on my Carvin Bolt 5 fretless. Very uprightish tone with really thick sound. I am pleased thus far. Have heard thenew ones have the same qualities.
TI JAZZ FLATS: Everything you heard is true. Low tension, pronounced midrange, very smooth to the touch (like touching glass, although you can feel gaps between the windings on the E and A strings). They are really in a class of their own. They worked really well on my 96 Fender Fretless P, which I alternate with......
SIT POWERWOUND NICKELS: Most underrated strings made. Lots of mwahhh, long lasting, and smooth touch. Go to rounds for my fretlesses from here on out.
Here are some other string sets I have used in the past. I do not currently use them, but someday may revisit them again:
GHS Pressurewounds: compressed strings with a smooth touch, which translates to easy on the fingers and the fingerboard. I prefer them on my fretted Jazz instead of fretlesses these days. Lot of love for them these days on TB, and not without a good reason.
GHS Brite Flats: Good sounding, but felt too rough and high tensioned to me.
D'Addario Half Rounds: Like the GHS Brite Flats (also a ground wound string) a great tone but a little too tension heavy for me, even in the light gauges.
Fender Flats: The old version was hi-tensioned and felt smooth to the touch, a great Motown vibe. The new models are less tensioned, but still smooth and thumpy. Probably the best price-wise of any other flatwounds mentioned.
Fender Tapes: I haven't used the new version made now, but the older ones were low tension, kind of like the TI Flats of the tapewound world. Not as smooth as other tapes, and has more of a "roundwound" sound than other tapes.
LaBella Tapewounds: Higher tensioned that the GHS or Fender tapes. A very good thick acoustic sort of vibe. Expensive, but you can get them from
Carvin.com - Guitars, Amplifiers & Pro Audio for a decent price, even with Carvin's expensive shipping charges.
D'Addario Chromes: Another flatwound set, but like TIs have their own sound, which is brighter than other flats and even twangy. The older ones seemed smoother than the ones made currently, but still have that same unique sound.
Good luck with your search for fretless strings, and I hope you find what you are looking for.