i went top tanga. largely bc i got it 1st, still miss top ari.
however, in my tests, patk + crit dmg is better than p skill power alone as far as the damage output.
what needs to be decided against is the reuse of ari. the extar skill reuse wont make a difference on any stab because they are typically ready to use again once you get to them. larger cool down skills it would be helpful on (angel of death, ue, etc). hide cant be made perma even with a top ari and the old refresh augs unless u crit hide, so thats a mute point on the reuse.
regarding skill power vs crit dmg on a dagger, crit damage scales better in my tests. this means 1% crit dmg > 1% skill power in dmg increase.
so, for which is better? both are good. imo the tanga will provide harder hitting stabs. the ari isnt bad tho.
the main thing is wait for a top grade ari or tanga, then invest in it. if you are lucky enough to have both top grade ari and tanga and tons of enchant pts, do u wanna crit harder or have angel of death and ue slightly faster? the 5% cool down just only affects like 10% of skills you use in a noticeable way.
i play more of a glass cannon style, so tanga works for me. ari is definitely the choice for yul and tyr tho imo.