Is it an AquaClear filter? If it is, then maybe the positioning of the intake tube needs to be properly seated or adjusted.
To the topic: I have used both and each have their pros and cons, but lately I seem to buy more AquaClears because I like the customizable filtration options and the durability of the sponge. You can really squeeze that sucker and it lasts forever before you have to replace it. My vote is for AC.