There can be a difference. I shoot a little over 70 pounds at my draw; and I shoot with two fingers. Fast flight string hurts my fingers so bad its not funny. You can put another layer of serving on fast flight to make it thicker; but I like an 18 strand flemish dacron string.
I can still hit stuff; the arrow might be slower; but my fingers are not sore.
I have cut a strand or two on my string; and it never happens at a good time. 18 strands gives me a little more confidence that way too.
Might be an illusion to think that; but I have had a bow string break on a draw; and had the riser snap in two ( Bear Kodiak takedown).