Quietness I'd have to concede, based solely on the fact each of us "hears" differently. Depending upon how old you are, and how much hearing you've lost, this can make a big difference. Evidently I've lost my upper range hearing more so than my lower, at age 46. Least that's what my wife and dotter say. Too many hours spent around loud motors and traffic noise in my youth I suspect. FF strings are smaller diameter, and consequently have a higher note or frequency, and this might account for my preference as much as anything.
In terms of total sound volume when you compare strings of equal mass, or a string/arrow combination of equal mass, I believe the difference is mostly one of harmonics, which can be mitigated with tuning. One would have to concede optimum tuning in each scenario, but FF does offer the advantage of lower overall mass, allowing one to position some of that extra mass in the form of puffs or "silencers" strategically to dampen the natural harmonic. It's a bit of a crap shoot sometimes admittedly depending upon the bow and arrow combo, but I've had better luck with quietness (given my unique perception of quietness) overall using FF, versus B50, particularly on high early draw weight bows.
I can see needing a fatter diameter to avoid splitting self nocks as well, but I generally double serve so that's a wash. Plus I use plastic nocks.
I'd never considered how a string that is heavier, and has more creep and has more stretch could be more accurate. Seems it would be a difficult thing to demonstrate, absent a shooting machine, and even then one must consider proper tuning is assumed in each scenario. No question that changing to a FF string would change the tuning significantly. I personally don't have great form, but I have no problem getting perfect arrow flight, and being able to shoot 50 grains more arrow and 10# more spine from the same bow, changing only the string as the price to pay. The only target archer I know well enough personally to comment on his preference (Jeff Gibson from Arkansas has won a few notable titles I think, lots of regional tournies) swears by, or did, Spiderwire endless strings (ironically). I don't think olympic archers go for higher mass, higher elasticity strings but I honestly don't know.
For the most part I prefer FF because it allows me to run a lower brace height and not interfere with my sleeves, wrist and thumb and because it dampens handshock in any bow significantly. For a tillering string, particularly on longer bows, B50 stretches so much, 2" to 3", I find it difficult to first brace a new, and accordingly extra heavy bow, because I have to bend it so far beyond where I would with a FF string to reach the string groove.
But I humbly concede to anyone's preference, just curious what, besides antecdote, accounts for the preference for heavier, more elastic bow strings.
George I like to challenge dogma, challenge people actually to evaluate or re-evaluate their choices, their options, their opinions. Time spent challenging one's assumptions, mundane things we frequently take for granted, is time well spent in my experience.