MAB normally wins unless your very starved on WSC or have ridiculous MAB
Base Magical WS Damage = ((152 + floor((WeaponLevel-99)*2.45) + WSC) * fTP + dSTAT + Magic Damage (Statistic)
Damage = Base Magical WS Damage × Magic damage multipliers
Assuming il119 weapon on TF at 1K TP (Gastro for 1250) and 350? AGI (guessing, don't know how much is standard for you guys right now) against a mob with 200 INT.
fTP = 4.541015625
BDMG = ((201 + WSC) * fTP) + dStat + MDMG
DMG = BDMG * mDiff * WSD * Weather * SDT
(201 + 350) * 4.541015625 = 2502 + 300 + MDMG.
2920 vs 3019 or a 3.3% difference, 34 MAB on a low MAB job like RNG will be far more important.
So with a WS like True Flight where your mod is 100% AGI and your dSTAT is also dAGIx2 on low MAB jobs like RNG / COR MAB tends to win over in most cases. Now these weapons aren't at max yet and I suspect another update or two will have them at 30 MAB, so lets see then.