What is the energy difference (energy output) in hydrogen burning in a fuel injection (combustion) engine and hydrogen used in producing electricity in hydrogen fuel cells? Gasoline power is stronger.

BMW has made a hydrogen fuel-injection based car, meaning this is not a hydrogen fuel cell, but the same engine used for burning gasoline, but now it burns hydrogen instead. The car is found here.

http://www.cars.com/go/features/autoshows/vehicle.jsp?vehicletype=concept&autoshowyear=2007&vehicle=concept_bmw_7hydrogen&make=BMW&model=Hydrogen+7+Prototype

What I am wondering is, that if hydrogen gas when burned is the same potent as gasoline, then shouldn't a fuel injection engine be more powerful than a fuel-cell electric engine? My particular interest if the two are different energies (battery cell vs. hydrogen combustion). If hydrogen combustion produces more horsepowers, then that extra energy could theoretically make up for the 30-40 percent energy loss in making hydrogen.