Hmm. It occurs to me that there is another factor at work here. Once again, using the guitar as an example, playing chords in flat keys gets you into barre chords right away, but for scale passages, it shouldn't make that much difference. A classic or jazz guitarist learns various scale patterns, and what key a particular scale pattern is in depends on where on the fingerboard you start it. Since the fiddle doesn't play chords that often (occasional double-stops), I don't see that it should make too much difference. But then, not being a fiddle-player. . . .

Don Firth