I like DwarfPool due to its full stats and ability to talk to operator if you have questions. Every share is logged, so any issue always can be fixed by recalculation. It is small (because it did not enter Zcash race in time). It provided 50% to 30% of Ethereum mining, but only 2-3% of Zcash at the moment. The more people will use it, the less will be variance in payments.