[Finger] All Races Experience point bonus: +50%
Maximum duration: 720 min.
Maximum bonus: 30000 LV 1 WAR MNK WHM BLM RDM THF PLD DRK BST BRD RNG SAM NIN DRG SMN BLU COR PUP DNC SCH GEO RUN <3/3 4/[00:15:0, 5]>
I actually find this to be much more convenient than the Empress Band. Seeing as how the effect lasts longer and how one can get more exp in one sitting -and on top of that, it only has three charges and I'll explain why that's good.
What I do is after receiving a tell for party invite, I use my Emperor Band's last charge, then I trade it to my nation's gate guard or Outpost NPC for full charges. After your initial exp bonus wears off after having fought in party, simply use it again for another additional 2000 exp. Works like a charm and I haven't thought to go back to Empress Band since.
To simplify things, if you party daily, the Empress band is probably your best bet. For those who party occasionally, Emperor is the way to go.
The two charge trick he mentioned bumps total gain on each to 8,000 a week if you know what you're doing, so really it just depends on your EXPing schedule.