Dude, strings are personal preference and rackets are too to a certain extent. But if you ask me, BG-66 are good strings. I just switched to BG-66 from the traditional BG-65.
Re: between BG-65 and BG-66 I personally find that the difference in strings are minimal and more impact towards your tension. I've used both the BG-65 and BG-66 and have probably not noticed too much of a difference in either one. I will be switching over to the Winex Ti-80 string to see whether titanium-laced string is better. I've also heard from some players on their impression of the BG-65 titanium in that it's stiffer than usual so they string the racquet at a lower tension than if they use a BG-65.