This is something I think about quite a bit... the long answer is, it depends.
I had some thoughts on it back when I recorded a set of fretless bass samples
My thoughts have since changed, after trying to apply those rules to a couple of other instruments and it not working nearly as well.
In short, if you can sample every note from the lowest range to the highest range - starting at C and ending with B, it will give you the most flexibility with chords (using n notation, rather than note).
The problem is, with most analog instruments there are often timbral/tonal variations that are important to have to really capture the nature of the instrument... which makes doing this whole process massive as you build multiple sets with multiple variations.
The flbass set was great because I didn't need a wide range of notes to still sound ok pitched up or down, and I got all the timbral/tonal variety in the one set - these work well with note notation
Some instruments just sound crappy once you start adjusting their pitch through playback speed though (sax, bowed instruments etc) - so you kind of need to pick a method based on what instrument you're sampling, and how the sound changes as you re-pitch.