Re: which is more important...
I don't know if there is a single right answer to this question. But I think pumping frequently is generally better for supply than less frequent but more complete emptying of the breast.
The PP asked some good questions about shield fit and pump function, above. Maybe there is something in your pumping regimen that can be tweaked so that pumping is more effective!
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"