Fast flight materials- little to near zero stretch allowing more consistent brace height retention- yes once Dacron stretches enough it generally stops but..., also more durable/wear resistant, and in my experience, unfortunately opposite to yours, reduced shot vibration/ hand bump/shock on every bow I have put it on and made them quieter. Fast flight to me has a higher pitched tone on the shot than Dacron, that very well could be what you're perceiving, but overall noise level should be lower with a properly made FF string on a FF approved bow. The comparison that proved my theory for ME was when I did the experiment on selfbows. Some guys swear up and down that Dacron is best for selfbows, but go over to Primitive Archer, almost all of them run FF if they use a man made material. Linen in medieval England was actually a no-stretch material, it either worked or it broke, and amazingly got stronger when wet. Animal sinew strings were also low to no stretch, so really FF is perfect for selfbows. I have taken hundreds of shots and never had a problem. Always noticed less vibration and noise. I actually have had so many frustrations using Dacron, whether it be stretching or inability to maintain exact brace each time stringing the bow, to abrasions, to increased handshock that I will happily accept rolls of the stuff to burn it. BUT everyone has what works for them. By all means, if you have a good thing going, keep at it. And yes, the speed difference is not that great if you use a FF string with same strand count as the Dacron, but go down in strand count and make it skinnier and see what happens. 10-12 is a nice number for a preview. If your bow is under 55# you can even try 6, its wild. Mind you, there are many different FF materials with different diameters. My personal favorite right now is Brownells Rhino at 12 strands.