+15% attack power or +15% dexterity

which will add more to my dps? also, does auto-attack benefit from attack power rating?
Thanks

AR improve your plain autoattack damage and skill damage.
DEX improve your AR (by half value), but also increase your hit, dodge and crit.
Which more increase your DPS you can find after a couple of tests.

PS i take both

AP/AR only affects your ability damage, not auto attack damage, it did in beta but they pretty much doubled auto attack damage+the auto attack boost abilities to compensate for lack of scaling with auto attacking now. the only thing that will upscale your auto attack damage is +% phys damage, or +% auto attack damage, +%critical damage boost, +%damage or +damage, -enemy armor/mitigation.

attack power will not increase auto damage. (the issue was it'd increase low weapon damage by X amount basically making every weapon upgrade extremely minor, IE +100 AR= +10 wep dps, add that to base 10 wep dps and you have +20 wep dps, upgrade a weapon to 13 wep dps its +23 dps. Now it's like +15-17 base wep dps with no scaling from AP)

Between those two I would take the 15% attack power until I got higher in level where the 15% dexterity would become more useful because your higher dexterity. At 50 I'd go with the dex because I am a crit addict and like seeing bigger numbers rather then higher average numbers. I also have points in Increased Fire Power which increases your attack power when you get a crit so.... I am a Marksman/Assassin/Ranger, level 26. I will be resouling the ranger once the pet becomes useless to either sabo for the % dex and aoe slow or nightblade for the % increased damage on combo point generating abilities. Could change my mind by the time I reach the point where I'll even be adding points into my 3rd soul....then again being a marksman that Riftstalker ability Shadow Shift looks awfully nice. Move 15 meters forward....