> They are frequently more prone to shifting as environments change
> They contribute less to tone compared to their thick-necked relatives
> Thin-neck basses give the impression that their action is higher when compared to thick-necked basses having the same string relief
> Having owned thin and thick-necked basses I don’t find thin-necked basses easier to play (I have average-sized hands)
I've owned not only thin (width at nut) but slim neck (front to back of neck) basses since 1966. Both have been passive Jazz Basses. The first was my 1965 Jazz that I bought in 1966 and the second is the bass I'm using now, which is a 1982 maple-necked Jazz that I bought in 1985 specifically because it has the same neck measurements as my 1965 did (60's slim C-shape with 7.25" radius).
• I've never had a neck twist on me nor even have a problem with one. They have been very stable and rarely need any adjustment.
• Tone is a combination of a lot of things including the woods used for the body and the neck as well as the electronics used. I don't need my necks to be chunky to get a good sound. I absolutely love the tone of my Jazz Basses. My 1982 jazz has a slightly brighter sound than my '65 did ('65 was stolen in 1976), and has significantly better sustain. I attribute the brighter sound a bit to the all maple neck, but mostly to the 70's era pickup spacing (4" center to center), which puts the bridge pickup closer to the bridge. I attribute the sustain to the all-maple neck and prefer the sound of my '82 to that of my '65.
• I use a low action and a light touch because I can control my dynamics more easily with that. Don't really care what it "looks like" to someone else, just how it suits my playing.
• I find the thin and slim necks far easier to play than the wide and fat necks. Tried a 1966 Jazz when those came out and it had a thin neck like Jazz basses up until then had, but it was a deep U-shape that pretty much made it unplayable for me, especially when I tried to play something above the 12th fret. Tried a cool pattern used in a song called the Tighten Up by Archie Bell and the Drells, where the bass plays its pattern starting on the octave F# on the E string (14th Fret). I had no chance of playing that riff on that '66 Jazz. I handed it back to the sales person to hang up on his wall and thanked God that I had 1965 Jazz instead.
I have never enjoyed playing P-bass necks either because they are so chunky. Then my Grandson got a Squier p-bass with P/J pickups for Christmas and I could comfortably play it. Was still the same width at the nut, but it was a slim neck, not a chunky one. I also have a 5-string that is 1.78" wide at the nut, but its a slim neck, almost as slim as my Jazz. Although it has a really flat radius (12") I still find it comfortable to play. So for me, I think the problem with playability is necks that are too fat, not necessarily just wider.
I also should mention that I not only played my '65 Jazz through high school and some college, I also toured with a nightclub group for 3-years in the early 70's, playing 5-nights a week, 50-weeks a year. So I got real used to playing with that thin, fast, neck. I spent almost 10-years after my '65 was stolen, looking for a Jazz with that same slim neck. Every Jazz I found was fatter and then they changed to a 9.5" radius (currently Fender's standard radius) that made them even more uncomfortable for me to play. So, I'm very prejudiced towards the thin, slim, and fast necks.