The greater the linear dimension of surface skimming you have the better you will be able to get laminar flow over the weir as opposed to pulling from beneath the surface for a given sump return pump flow rate (assuming your plumbing can accomodate the desired flow rate). More laminar flow over the weir ensures you're preferentially pulling the proteinacious film off the surface of the water.
So go with B and definitely don't go with one overflow unless it's coast-to-coast (or near cost-to-coast).
I don't know how much room, if any, you have behind the tank but take a look at this site for a good overflow design (it's also a good site for others to get a handle on how to improve efficiency and safety in their overflow design):
http://www.beananimal.com/projects/s...ow-system.aspx
There is a thread in the DIY section of RC with more pictures and discussion if you're interested.