I am not the OP but I was wondering almost the exact same thing for myself.
I am Windwalker.
My guild is working on Garalon normal, should have it down after the holidays. So Empress should be a few weeks away, but then I have competition for the fist weapon. Stone Guard/Feng heroic are in reach, Gara'jal probably not.
I've been wondering a similar question about claws of shez'keer vs gao-rai. both normal. Rolling with the claws atm for both Brew and WW. Seems to do alright, but I can't help but feel I might be missing out, especially as I've upgraded the staff twice.
Generally, higher ilevel = win. But in this particular situation, there's some over-riding factors.
Higher ilevel = more weapon DPS. I am unsure of whether that's enough to beat the 500 agi gem, but I'd wager it is. I also don't like the idea of ilevel upgrading raid finder gear... Doesn't sit right with me. Besides, dual-wielding is the better option for DPS, so here you should go with 2x gara'kal.
Weapon DPS does nothing for our personal survivability (it would indirectly increase the strength of the Guards we put on the raid, but that's a minor boost), so for here the raid finder staff with the 500 agi gem would win easily. Agi is great for reducing damage taken, so yes: staff.
Considering your progression, ilevel upgrading the staff would be viable I guess... You're unlikely to replace it anytime soon. Up to you on that part.