Choosing a filter for your Synthetic Oil

That's a really good question ; @ first I figured, just get the filter that has the best filtration level (lowest/smallest micron particle rating) , but that then may also restrict flow volume...?
Then comes in the advertised additives released by the filter...are they needed, will they help or hurt the synthetic oil ?

I use Royal Purple, and I will ask them for there view on this, and I will be following this thread as well.