I was forced to make the same decision not so long ago and I opted for the Mastersound A Customs because they had a more defined foot chick. A Customs in general are thinner than New Beats (med-thin top/medium bottom vs. medium top/heavy bottom) so it should come as no surprise that some of the heft will not be there on the A Customs. Taking the Mastersound option fills in some of that gap. I had the ACMS hats and NBs and loved them both, but the ACMS hats were more sensitive and once I got used their lighter playing, came to prefer them for many things.
I never considered the reg AC hats, though. My experience with them is that they didn't have as much cut as I would have liked. They actually felt weak to me, but I don't gravitate toward sloshier hats anyway. If that's your thing, then maybe the regulars will work for you better. Best to keep these things in mind when you go try them yourself.
The A Customs made now are thicker than when they first came out and the hihats are no exception. I had a pair of the 13 " A Custom Mastersounds from when they were first introduced and I was shocked at how much heavier the new ones are.
The A Custom mastersounds are great cymbals- the foot check is really pronounced and they have a great sloshy half open sound.