A 90 degreeg V8 does have better tertiary balance, at the cost of a crankshaft that weights at least twice as much and a bit of boxing horizontally across the centerline of the engine, and a burble in the 'note' of the engine. A 180 degree 'flat' plane crank, is lighter, stronger, and does not have the boxing moment that the balanced V8 has. The (properly balanced) flat plane V8 has just over 4 times the vibrational energy of the (properly balanced) 90 degree V8. Beyond the savings in weight and rotational inertia, what is gained is even intake intervals and even exhaust intervals that make it much easier to extract power from the harmonics of the intake and exhaust processes. Nobody driving around in a V8 Ferrari complains about the slight loss of smoothness of their flat plane V8, no, they notice the glorious sounds that eminate from the engine bay. In the powerband, and F1 engine is between 107 and 113 percent efficient in the volumetric department! You can't do this at the RPM levels of F1 with a 90 degree crank V8; however, you can do this with the RPM levels of NASCAR engines by threading one of the header tubes from each side under the dry sump. The V10s were balanced with balance shafts turing at 2X the RPMs of the engine. This sapped power (maybe 30-50 HP) that could have been liberated towards thrust if the V10 engines had better inherent balance. So the solution here, was "not efficient" in terms of converting the energy of the burning gasoline into thrust for the vehicle.