I guess we would have to sit down and figure out the wsc for AP.
I know str definitely plays a role in, I am just not sure if its str/dex, str/agi, just str etc.
Knowing that would help a lot in deciding which is better.
While this is all true, as a practical matter I'm not sure how important it is. Might be interesting to know more about AP, and atma does help to more easily test which stats are important since we have atma with such large chunks of stats. But when it comes down to it, how often are you in situations where the ONLY thing that's important is maximizing AP numbers? Not saying figuring out more about AP isn't useful, because it clearly is - but at best it's just one consideration in the whole picture.
The real practical question is which combination produces the best overall master+puppet results, not which atma is ideal for Armor Piercer only. Plus, even considering Sharpshot alone it's not all about AP. GH would impact melee crit rate, ranged accuracy, and survivability with some more evasion and the occasional counter. VV would give a little bit of regain, 5% DA, and the extra STR (which would probably be most noticeable on WS damage). At any rate, either one is clearly a good DD atma, but I think only considering AP damage is oversimplifying things a bit.
And it gets even more complicated with a new WS coming in a week...