i have or had a majority of the numbered series balls.
the 500 & 700 series are proven series
the 900, not so much, the 912T is the only one so far that may be the real deal as far as the 900 stuff being stronger than the lower numbered ones.
300T is a great ball for thr short sport
505T, 503T,505c, all great versatile pieces for medium patterns
715T,715T, really good for the higher volumes
Me personally, i do not have great reaction with much of the "A" balls
have had several, they just move off the spot to quick for my game
the 916 & 919 were not what i was looking for at all. got rid of both right away
got another 715t instead