Les in Chorlton

In attempting construct a "fair test", ie to control as many other variables as possible, can anybody who has played say 2 instruments to about the same level and practices and plays them as often comment on differences that they have found?

Not sure that I can quite fill the bill. I play fiddle and English concertina but not necessarily to the same level. I'm faster on concertina then fiddle which I think is partly due to greater experience but also the fact that the mechanics of playing are less complex and involve smaller movements. In southern English music (Sussex unofficial motto "We wun't be druv") speed is less important but the differences may apply to accuracy and expression.