[Question] Jewel Setting

I saw a lot of Slayer running around with both weapons 36% SoulLeech or 72% PvE.

I've been playing on other Pservers and i know only the Jewels from the first hand weapon are used.
But Mazey Flyff is way different to others, so my question is:

Does is make sence to put in both weapons the same jewel effect ?
I always used SL first and when i dont need it change to PvE.

Does is make sence to put in both weapons the same jewel effect ?

NOPE! Only works Jewel upgrade is the Primary weapon for Slayer Only.

Having two weapons (Slayer) w/ SL% and PvE% for Switching Tactics for B-mobs Hunting.

and also Slayer player they jewel Upgrade their Weapons w/ PVP% and PvE%. They can PVP and PvE (Switching Tactics)