avent for sure
my wife got the medela double pump thinking it's the best since hospitals and friends recommended. this was before our son was born. unfortunately, we had to see a lactation consultant shortly after our son was born. the consultant is using avent pump and my wife gets to try it. since then, we haven't looked back. the avent pump is the way to go and here's why :-
* it has a massage function which helps to simulate milk flow
* the pump is programmable. didn't know breast pumps can be so high tech. this is useful to simulate let down followed by how hard/soft you want the suction to be. something like 2 hard suction followed by 1 soft? you get the drift
* no doubt that the medela is more powerful but this is not necessarily a good thing. for my wife, the suction was so powerful that it actually cause slight pain and hence uncomfortable. if you experience that, then naturally you get nervous or uptight about it and therefore, the milk flow is crap. milk flow best when one feels comfortable and at ease.
after switching to avent, my wife is getting more milk than before. also, get a single pump. double pump is not practical as you would need the other hand to help press/guide the milk from the glands around the breast to the light at the end of the tunnel.
hope this helps!