"What do you Hill shooters use B-50 or fastflight on your bows?Which is more quiet?Which do you prefer and why??"
I don't shoot a "Hill", but I have a few selfbows that are straight or mildly reflexed.
Quiet is a matter of tuning. Pitch is differenct from one material to another, but with proper tuning most any can be made very quiet.
HMPE materials (Dynaflight '97, 8125, Fast Flight, etc.) are much more durable, have less stretch/creep (so your shot is more consistent), and can help reduce shock. I've never seen proof that it will reduce the life of a bow, if the string and bow are made properly.
The only way to know for sure what you will like best is to try a few different ones.
Chad