Well the argument is over where do you get the most fruit flavors. There are those fighting for primary and those fighting for secondary. The discussion seems to be that some people think that if the yeasties are allowed to eat up all the sugars in the must, than racked on top of the fruit, then the fruit should impart more flavors.
Personally I don't know, there seems to be little evidence either way, so my solution as to do both (as advised by another memeber, Pyro). I did 4 lbs of blueberry in primary and will be racking on top of 3-5 lbs more depending on how much flavor I want to add.