My experience is that it all depend son the day. Many days it doesn't seem to matter.
I go to one pond, that if I hit the right day, the fish a keyed in on a midge.
Size 20 hook with golden pheasant tail fiber wrapped on it. The ill hit that regularly and seldom take anything else.
Any other time the fish will take most flies.
Think this is why they call it fishing and not catching.
Rick