How Much Do WS 'mods' Really Help?

Wondering say for using a WS like Slug Shot, the mod is AGI:30%. For COR, I don't have Crimson yet so would it be better to use say Pallas (STR+9 AGI-5) or Mage's Cuffs (AGI+2). Assume my acc is good and don't need the AGI for that. Will the -AGI hurt more than the extra STR will help?

If you want to approximate the impact of STR on a ranged WS negating ratk gains, take it as if it had a 60% WS mod (at 75).

If you want to approximate the impact of STR on a melee WS negating atk gains, take it as if it had a 30% WS mod (at 75).

That basically means in terms of pure WS mods, every 1 point of STR is worth 2 AGI. So STR9 AGI-5 in AGI terms is AGI18 AGI-5 or AGI13.

EDIT: Note that I mean if there is no actual WS mod in the first two sentences and that fstr(2 in ratk's case) is not capped.