In the current corn process, you grow a whole stalk of corn, take off the ear, shell and mill the grains, break the starches down to sugar and then ferment. A lot of energy went into growing an 8ft tall, rigid plant, but you only take energy from the grain.
In comparison, converting cellulose directly to a usable fuel could yield much more energy from a given plant. The plant body is very high in cellulose, giving it a rigid structure. Even for corn, there is more energy stored in the stalk than in the ear, but previous processes for converting cellulose to a usable fuel are too energy inefficient, using up more energy in processing than you get out in fuel. The goal of the recent biofuel research is to find an energy-cheap conversion from cellulose to fuel. That would improve the overall energy balance (energy in the fuel minus all energy used to produce the fuel) for biofuels. The more net positive this balance is, the more benefit from biofuels. Moreover, hardier crops such as switchgrass and sorghum could be grown for cellulose. These crops can be grown on poorer land with less fertilizer and less care and easier harvesting.