My Main Fretless is a 2007 Spector Euro Bolt-On 5 DLX FM with an Alder Body with Flame Maple top in "Black Blueburst" (it was, and to a degree still is the "Sister Bass" to my 1st fretted Spector in "Black Cherryburst"... back when I though 2, perhaps 3 with a four-string were all I would need. Hahahaheeheehee... HAHAHAHAHA!!!!) I have Five Euro Bolt-Ons (...and a "Spector Legend Custom" 6-String I got for a song...no, rather a jingle: a "Level 1" Return to "Musician's Friend", no dings. no build issues... that allowed me to graLegendb it as they were removing the entire line from their Stock... And allowed me to purchase quite literally "Their Last Bass" at about 68% Off MSRP! ) as there is no 6-string in the "Euro Bolt-On" line & a Sixer from the "EuroLX" is far above my needs percentage-wise, financially or construction-wise as a Neck-Thru as opposed to my desire for Bolt-On Basses) with either Flame Maple or Zebrawood "full-on" Tops: on over half of them, the Top wood is actually thicker than the Back wood of Alder - pretty much the opposite of "veneer". A 3-piece Maple Neck, 35" scale with the Spector Deep-Set bolt-on 3-piece Maple Neck, Rosewood Fingerboard and an HG Thor Epoxy coating ("Mwah for Days"). I've gutted the Gotoh GB-7s for Hipshot HB6Y Ultralight "Y-Key" Tuners & the stock electronics for Custom EMG-sized & custom-wound Nordstrand Big Singles with Aguilar OBP-3SK/PP so they sound even more like "a Spector on J-Bass Steroids" than a USA NS-2J.
My "Second Fretless" is a defretted 2005 Fender Jazz 24, which was a downsized, 24-fret model Fender made from 2005-2010 much like "Dinky J-Basses" made by other companies... including Fender's "Deluxe Jazz"/"American Deluxe" Line of USA-made 22-fret downsized Jazz & Precision Basses made from 1995-to-2008 before reworking the lineup. I purchased this not 2 weeks after purchasing my Fretted version, liking the playability, tone & options at its price-range on the Used Market and deciding I was going to pick one up, have it defretted by a local luthier friend of mine, and have a 4-string Jazz Bass Fretless in "My Toolbox". He did a wonderful job, and it's great to have the 4-string Jazz with a Hipshot Bass Xtender option
The Jazz 24 has a 3-piece Alder body with a Quilted Maple veneer, Maple Neck with a satin finish, Rosewood Fingerboard and its own version of a "Deep Set" neck joint, connected by long, 6-bolt neck plate. Made in Korea, it came stock with licensed Hipshot Ultralite HB6C Tuners, a Heavy-Mass Bridge with String-Thru-Body or Thru-Back options, real MIA Seymour Duncan Bassline SJB-3 "Quarter Pounder" Jazz Pickups, Duncan-Designed 3-band Active Preamp w/ Passive Bypass on the "Push-Pull" Volume Pot, and "Slap Switch" which removes a large amount of midrange frequencies and boosts the Low & High-Range, which does indeed help in making the change to Slap-style playing a "One Control" change.
In regards to both Basses, overall Tone & String Choices I think of myself as a "Rock Bassist", so I use D'Addario XL Nickel single strings to make my own personal Balanced Tension Set - with the Spector fingerboard coated in epoxy and the Fender's stabilized in numerous coats of Tung Oil, I don't feel the need to be overly cautious in terms of using coated strings or other type of specialized strings. I simply feel that the XL Nickels are well-balanced both sonically (but *do not* want the "piano lows & chime" I prefer on some of my "more aggressive" Basses using "D'Addario's ProSteels") as well as in terms of tension with the set I've put together.
Hopefully in the near future I'll be adding a Mike Lull Modern 5 Fretless to my both my Lulls as well as my fretless basses, but until then I feel I have things pretty well covered between my Spector fretless 5-string and my Jazz 24 fretless 4-string.