A VX forum member posted link to this study a while back, can't recall who it was, but it certainly gives you clearer understanding of the differences between oil filters and confirms there are big differences.

http://people.msoe.edu/~yoderw/oilfi...lterstudy.html

I just picked up a Royal Purple oil filter at Pep Boys, first time I've seen one by RP. I'll use it next oil change.