Originally Posted by wombatclay
It depends on what you need the pump for (will you be pumping several times a day? once a day? do you have access to an outlet where you'll be pumping?) and on how you react to the individual pumps.
If you can, try out a few different pumps...I found that the Avent Isis worked really really well for me despite the fact that I pumped twice a day 5 days a week for over a year. Even though it's a hand pump (so most people wouldn't recommend it for daily pumping) I got 5-6 ounces per breast in about 15 minutes with it. I tried an electric pump for a while and got less milk in the same amount of time (plus it was noisy and meant I had to either burn through batteries or find an outlet) so I stuck with the Isis.
But every mama is different and a pump that works like a charm for one mama may not work so well for another! The only thing I'd suggest (other than trying different pumps to see what worked best for you) is to avoid the manual pumps that are made by formula companies. They aren't motivated to produce a great pump (since a frustrated mama might turn to formula) and I've heard some negative feedback on the quality of those pumps as well.