I go with PPLNS or some variation of it based on the pool. PPS is good if you can not mine almost 24/7. I have 3 USB erupters and have mined on btcguild, slush's pool, and bitminter. BTCguild has a very high hash rate and finds blocks early but pay is low and transaction fees are high. I spent a majority of my time on slush's pool since the fee is 2% instead of 3%. I am now on bitminter and love it. The main reason is switched is namecoin merged mining. Its like a very small bonus but any bit helps when you are not mining with a lot of hash. They also only charge 1% fee.
PPS looks good however since they have a higher risk the fees are huge so for me this was a turnoff.