first and foremost - if a bow can handle modern string fibers (high modulus polyethylene, aka "hmpe" and brand names such as fastflight, dynaflight, astroflight, etc), DO use those fibers and don't waste time with dacron (polyester). the prime advantage of hmpe bowstrings is *consistency* due to low stretch and creep, and higher tension per strand that allows for low strand count bowstrings.
i've spun up thousands of bowstrings over the decades and i started off with brownell b43 dacron because it was the only most viable game in town. for way more than a decade i've been using bcy fibers exclusively for all the reasons chad has mentioned. ray and company are great folks to deal with, and will go out of their way to tailor the fiber to yer liking - as they did with me and dynaflight'02, which is a low wax version of dynaflight'97 that's made for spinning and not twisting, and yes it can be special ordered even if it's not listed in their catalog.