Comparison of mining pools
Reward types & explanation:
- DGM - Double Geometric Method. A hybrid between PPLNS and Geometric reward types that enables to operator to absorb some of the variance risk. Operator receives portion of payout on short rounds and returns it on longer rounds to normalize payments. 
- Prop. - Proportional. When block is found, the reward is distributed among all workers proportionally to how much shares each of them has found.
- PPLNS - Pay Per Last N Shasres. Similar to proportional, but instead of looking at the number of shares in the round, instead looks at the last N shares, regardless of round boundaries.
- PPS - Pay Per Share. Each submitted share is worth certain amount of BC. Since finding a block requires <current difficulty> shares on average, a PPS method with 0% fee would be 25 BTC divided by <current difficulty>. It is risky for pool operators, hence the fee is highest.
- SMPPS - Shared Maximum Pay Per Share. Like Pay Per Share, but never pays more than the pool earns. 
- ESMPPS - Equalized Shared Maximum Pay Per Share. Like SMPPS, but equalizes payments fairly among all those who are owed. 
- RSMPPS - Recent Shared Maximum Pay Per Share. Like SMPPS, but system aims to prioritize the most recent miners first. 
- CPPSRB - Capped Pay Per Share with Recent Backpay. 
- POT - Pay On Target. A high variance PPS variant that pays on the difficulty of work retuened to pool rather than the difficulty of work served by pool 
- Score - Score based system: a proportional reward, but weighed by time submitted. Each submitted share is worth more in the function of time t since start of current round. For each share score is updated by: score += exp(t/C). This makes later shares worth much more than earlier shares, thus the miner's score quickly diminishes when they stop mining on the pool. Rewards are calculated proportionally to scores (and not to shares). (at slush's pool C=300 seconds, and every hour scores are normalized)
Source : https://en.bitcoin.it/wiki/