Guys is ethermine.org still one of the go to pools for ethereum mining?

I always have about 96% accepted shares and 4% stale shares .. ? Why 4%? Is that the miner fee?
What does stale mean in this relation?

I mean the weekly outcome is good but slightly below of the whattomine calculation with my "reported" hashrate from my rigs.

All rigs perfectly stable since the last restart one week ago. No disconnects, restarts, etc.

Any help or info for me?

Thanks a lot!