I'm not too clear in my own mind to be honest...


But one key factor should be the different dimensions of fret wire
ie.. thin, fat, high, low...???

Some guitarists play with a light touch, others dig in
pushing the string right down deep into the wood of the fretboard.

I've got guitars with dodgy intonation where I've got to be careful
not to fret too tight and noticeably sharpen the notes
around the regions of the bridge or the 12th fret..


[btw.. something in the back of my mind, but probably not that relevant to this discussion.. ???

Newtone Strings :

"With the popularity of dropped and altered tunings we often talk to players who assume that they will achieve a lower pitch simply by buying a thicker string. Often this does not solve the problem because the core wire in the thicker string is the same diameter as the core in the standard string, and therefore will feel too slack if a considerably lower tuning than standard is desired. So we make a string with a larger diameter core which will tune to the desired pitch and still have the tension of a standard tuning string."]