Just depends on the setup and the player. Some players have been switching back to flatwounds, halfrounds, etc... Not my thing, but that sure would change the sound.
There is nothing wrong with fretless Steinberger, damn fine instrument. As long as it's the REAL Steinberger, not the cheap wood version.
Now the new SB synaps I am not a big fan of, just because of the demo video. Don't know if it was the player in the demo, or the new instrument, but it just didn't do anything for me.
I have owned a couple of fretless / headless basses, loved everyone of them. I prefer carbon necks and boards, nothing like the growl of carbon. I have played, but couldn't afford a real steinberger fretless, it had the growl even with dead strings.
You find the real deal, you won't be dissapointed. You also won't be buying anything else for a while, they are very expensive.
Good luck.