I was reading an article by Eric Borneman in which he said for any significant nutrient export the volume of the fuge would need to be as large or larger than the display to be of great significance. The majority of the same export would happen in the display anyways.
http://www.reefkeeping.com/issues/2003-12/eb/index.php
Myth 13 discusses this.
I do see the benefit as far as pods etc but I'm not sure how many make it alive into the display from an in-stand fuge after passing through a pump. I likely will have one because every little bit counts and it will up my total volume and stability.