Does worn haste affect special attacks' reuse timers?
I'm pretty sure fbss is a marginally better choice in terms of raw autoattack dps, but you are going to be losing 15 str and 8 ac to get it, whereas the rfs is just a pure upgrade. If haste affects your tiger strike and flying kick and whatever though, then it fbss would definitely be the way to go.
Edit - best I could do with a quick search was
http://www.project1999.org/forums/showthread.php?t=6716 where a few people all say that haste boosts melee special attacks, and no one says it does not.