24 frets or 22 frets ?
I agree on the fret spacing. The fret spacing is the same as long as the scale length is the same. However neck length may differ to allow better access on 24 fret necks. Making the neck longer and less stiff will affect tone.
I also agree that the tonal difference is not just with open strings. It occurs all over the fretboard because the pickups on 22 VS 24 fretters will be in different positions in regards to the fretted note. Everthing else being equal, the neck pickup on a 24 fret will likely sound brighter for the same note since it is closer to the bridge than the neck pickup on a 22 fret guitar. I was just disproving the harmonic node theory, which is the reason some people *think* 22 fret guitars sound better.
I don't think you can compare the a Jem to a Strat. Like Jay pointed out there are too many other factors affecting tone. You CAN'T ignore the difference in the comparison. I believe these factors, especially the pickups, impact the tone as much or more than 1/2" of pickup placement.
I have never heard anyone say a 22 fret Les Paul sounds like a strat!