Nice encapsulation, Dazbo. Thanks. I think it is true that many tunes seem to "lay better" in some keys than others, but it is a matter of a very subjective sense. Choice of key also depends on the instrument(s) on which the tune is to be played. That, I think, is true from the perspective of both the player and the listener. And then, there are always the matters of tradition, convention, idiom, and the like to be considered. I guess there clearly is no simple answer beyond "what feels good to you."