Sharon>> I used Medela PISA (pump in style) for both my #1 and #2. It's a good pump as it has a very strong and lasting motor, and it is very effective in drawing out milk..even better than the Medela FS (freestyle) according to the lactation consultant in TMC. The down side of Medela PISA is that it is very heavy, much heavier compared to FS. Most of my frens use either Medela PISA or FS. Btw, PISA is recommended by the lactation consultants in TMC.
I've not used Ameda or Avent before. What I heard from frens is that Ameda spoils quite easily. As for Avent, I heard that the manual pump is quite good.
Actually, I think that overall, our babies are the best pump. For my #1, I exclusively pumped (i.e. I didn't latch bb) and for #2, I did a combination of latch and pump. For me, I'm the type that is super prone to blocked milk ducts, mastitis (i.e. infection of the breast / milk ducts) and I find that even a good pump like PISA sometimes cannot clear the blockage. But my #2 is a wonder pump - I only need to latch her for 10 min and she can clear off all the blockages that I've been trying ways and means to clear on my own (i.e. massage the blocked age, squeeze, pump etc.)