Pplns vs pps, is often the answer. In a pool with pplns - Pay Per Last N Shares - we build up over rounds(N) our share in the reward(block). Suprnova uses 20 - 25 rounds for N. Threeeyed is another pool that also uses pplns
PPS - Pay Per Share, the sum of our submitted (accepted) shares divided by total submitted shares on the pool by other miners, gives us our percentage of the next block.
Pplns will give us more rewards in long term mining. [https://minergate.com/faq/difference-between-pps-and-pplns Read more here]