If you want to earn as many bitcoins as possible over time, go with a pool like BitMinter which pays out income from transaction fees and namecoins, and is also without mandatory fees.
If you worry about payments varying from day to day, you may feel that it is worth paying fees, and losing namecoin and transaction fee income, so that you know in advance what you will get every day. You will get less in the long run. But if you are on a tight budget and need those coins to pay the bills every month, you may need PPS to stay safe. As they say, "it's expensive to be poor."
After you leave the pool you are also still getting paid for a while until there is none of your work in the eligible shares/shifts.
In other words, if you already left, be sure to check back in case we found some more blocks before your shares dropped off the last 10 shifts.
IMO, BitMinter is the best pool to mine at for maximum BTC for your hash power over time, but the variance of non-PPS also tends to be like an emotional roller coaster. Some days suck beyond measure, some days are about average like PPS, and some days are absolutely amazing.