Oh now I get it, wow this is really something to think about, but yea I don't feel the difference, I have my old 1980 Series 1 4 string, and Anniversary 5 string, never notice that.
But this is a really interesting topic.
I also have few 5 string basses and when I play them I can't seem to feel so much difference between 19mm, 18mm, 17.5mm, well sometimes I do.
For example I have Yamaha TRB6P that has really wide neck, and I feel like it's 18mm spacing because of a wide neck, so after playing that bass and comparing it to my Ken Smith 6, seems like Smith is also 19mm and it's actually 18mm.
Also with my Fodera that is 19mm feels wider than my MTD which is also 19mm, but Fodera is 33 inches and MTD is 35 inches....
So I think it's different on every bass, also it has to do with whole ergonomy, string height, pickup position, how is the shape of the neck, all of it.
Few days ago I realised that my 1966 Jazz has 19.5 mm which I though always it's 19mm.
So just to sum it all, I really don't feel the difference, maybe I should talk to my fingers about that
