Agreed.  So that's what I did.  I have two GTX960 cards of the same make, and after making sure that the core and memory clocks were the same, set one to work on Nicehash and the other on zpool.

My setup was using NemosMiner, and I had customized each pool to my liking (select algorithms, minimum mining duration) and leaving it to NemosMiner so neither of the pools got to pick the algorithms for me.  Your mileage will definitely vary.

I wasn't as scientific as pikachuy, and went by the total unpaid amount on both pools as opposed to waiting for an actual payout, and recorded the amount earned over four days.  That was enough to show zpool at 10% higher in terms of unpaid amount.  It would actually go back and forth between the two some days; NH earning more during the day and zpool more at night.  Anyway, I believe zpool pays you precisely the indicated amount (fees taken off the front end) whereas Nicehash takes it on the back end which would result in 4% less (I use an external wallet) of a payout from the value shown.  So net to me should be approx 14.5% higher with zpool.

Anyway, four days was enough for me and I moved the rest of my GPUs over to zpool.  Zpool also pays out at lower earnings (weekly at 1.5 mBTC, vs 10 mBTC for NH).  Plus, with zpool being in Canada and Nicehash in Slovenia(?), the pool's profits (including the mysterious 20%?) are a little closer to home.

Oh yeah, I elected to be paid out in BTC.  Getting paid in other coins on zpool involves an additional exchange or something and would most likely reduce earnings.  I think that's what was said in the many pages of the zpool thread.  Please fact check at your own discretion--I'm just some dude on the Internet.

.earl