The first area that I see with filter quality, is the weight of the container the filter is built into. Some are solid, others are damn near the weight of a beer
can you could crush on your head
. A heavey weight, means a quality machining, thius a qualtiy fit of the parts
internally and a quality fit externally to your engine
. I have seen on poor filters, poor threads and internal bypasses that are made out of the same grade of metal the cannister is made from. Thus a chance it may operate poorly. Filter paper quality is probably the biggest aspect. Some papers are better than others.