May,
Intuitively, we will say electric pump is better. However, I do know of someone whose breast doesn't respond to electric pump but only to the Avent manual pump. So, what she did was to get 2 of those manual pump to make pumping session more efficient. And hey, she breast feed for very long! Definitely more than a year. So, it all depends. In my case, I have tried both and I will still stick to electric pump for efficiency. I used the manual pump exclusively during my work trip to just maintain my milk supply but it was really tiring and slow.