Current used local Craigslist inventory I'm considering:
Music Man Sterling (US) unlined with side markers ($600)
1990 Fender Jazz (Japan) unlined with side markers ($450)
2010 Fender Jazz (MIM) lined with EMG JVX pups ($375)
Thanks again for any help/opinions
All seem like good choices. They're also all likely built well, though their condition will vary based on the previous owner(s). It may just come down to your preference. Here's my opinions.
I'm not sure if the MM Sterling has one pickup or two, if it only has one, I'd strongly recommend a fretless with two pickups (a bridge and a neck). The bridge will be the best to accentuate the fretless mwah, but the neck is good to get a closer to DB sound, or take away the mwah if you want a closer to fretted sound, which may be good depending on the song.
If the EMG JVX pickups are passive and if there is a preamp in the MIM jazz, you may want to install a preamp bypass switch (if it doesn't already have one). That will give you the most versatile options.
You should probably just go and check them out in person. If you're checking out the lined one, remember my previous advice to run your finger along the fingerboard to check that the fretlines are perfectly level with the fingerboard. If you feel any humps or grooves at the lines, you may want to pass. Unless you don't mind relevelling the board, which will only cost like $40 with a radiused sanding block from stewmac and sandpaper.
Also, when you're checking out any fretless period, you should be inspecting the condition of the board. If the strings have left any deep grooves in the board, then it may require some relevelling as well. All fretless basses will have some light scratches on the board caused by the strings, these are fine. I'm talking about deep grooves here, like ones that if you ran your finger over them you can feel that the board is not level in that location.