It should be noted that these three tools have or may have 'house style' settings which could control the spacing. A first reaction I received explains that Finale has as much control over individual spacing as Score and of course with the added simplicity of setup via a panel. Details coming up...

The samples show that the tools react differently on accidentals which are a sixth apart (bottom accidental under or left of the top accidental).

Kerning is quite different as well, Finale's default putting the lower accidental too far to the left.

While Score keeps the distance between a note and its accidental fixed when outlining, Sibelius makes the distance depending of the available space: dense texture will cause the accidentals to hit each other. To avoid this, sufficient space was given.

Reactions to this subject are welcome and they will be incorporated in this page with due author reference. Please use the Score forum to comment or, alternatively, contact me personally.