This is why I said earlier in the thread that merits are subjective to whoever is using them.
It's not so clear cut when you compare the airy concept of value between AS and AC. One increases your damage on use (assuming that you weren't going to triple attack anyway, something worth considering in abyssea) and the other is a utility that provides a somewhat accurate dispel and infrequently a buff. They each measure their own worth differently as well.
AS shines more when you're solo or don't have a dispel, e.g. snatching the ice spikes off an enemy before you even engage it (I find the buff steal to be too infrequent to factor in at 1/5). It's more notable on enemies that don't have an item up for stealing of course, but it's really useable anytime something is buffed.
AC is a strictly damage enhancing tool, and therefore it's effect is much easier to calculate directly. Yet it has it's own considerations: the timer limits its potential on any single encounter, and it's difficult to say where a reduced recast would actually have significant effect on whatever situation you're in. On top of that, as previously mentioned with abyssea triple attack rates, it could be considered to have no effect from a math standpoint if the attack was to proc triple already. Triplus, AoA, AF3+2 head and merits place you at 31%, more if you use AaO, so it's certainly more than negligable in an abyssea setting.
The point is that without examining the circumstances, I don't think saying that the lowered recast on AC is better than the entireity of AS is meaningful at all. A case could be made for both, and I don't believe one is definitively better than the other in a general case.
Everything above concerns 1/5 AS vs. not meriting it at all in favor of 5/5 AC, for clarity
Edited, Jun 12th 2011 2:41am by TheBadShadow