Hey guys, I've been heavily researching constructing a 30 gallon sump for my 125 gallon tank and I've run into two basic designs, one of which is far more common and the other of which has far more bio filtration. Here is a rough sketch of them I did in MS Paint =)

Design A is the one you see everywhere in which the inlet is covered by a filter sock and then a baffle separates that area from the drip pan, mechanical filter, and bio filter area. This design sacrifices a large amount of the tank for a seemingly pointless chamber.
Design B forgoes that chamber and the water simply pours straight into a filter pad/drip pan/bio media chamber. This allows for far more bio media and I can see nothing wrong with this design.
Of course, I've never built a sump and therefore may be missing some obvious reason for which everyone chooses design A over B. Can someone please enlighten me?
Design A is the one you see everywhere in which the inlet is covered by a filter sock and then a baffle separates that area from the drip pan, mechanical filter, and bio filter area. This design sacrifices a large amount of the tank for a seemingly pointless chamber.
Design B forgoes that chamber and the water simply pours straight into a filter pad/drip pan/bio media chamber. This allows for far more bio media and I can see nothing wrong with this design.
Of course, I've never built a sump and therefore may be missing some obvious reason for which everyone chooses design A over B. Can someone please enlighten me?