Why not both you ask????? One answer is that best possible from corn is around 20 gallons/acre/year while algae offers more like 20,000. Producing ethanol from corn is basically a criminal activity; anybody caught doing it ought rightly to be hanged.
20 gal/acre/yr? Ethanol? Current corn-based yield in high corn-yield areas is at least 500 gal ethanol per acre per year with about 2,500 lbs of high-protein animal feed/acre as a by-product.
Your ethanol yield estimates from corn are addressed rightfully above. In addition, algae is being proposed as a source of biodiesel, not ethanol. I will believe the yield estimates once pilot experiments are scaled up.