I have 9 (I think) old Bear recurves, 2 new Bear T/Ds,
A Howard Hill "Mountain Man" longbow, and 2 custom R/D longbows
The old Bears, and my Hill longbow, have always had dacron strings.
My custom longbows and Bear T/Ds came with FF strings. I never liked the FF "skinny strings"
I switched my custom longbow strings to dacron years ago, and plan on doing the same with my Bear T/Ds soon.
Dacron is quieter, and I find (for me) a thicker string is more comfortable for me to shoot.
As for speed?? I could never really tell the difference....
I've actually been thinking of going back to endless loop dacron strings?
They were all we had when I was a kid!