There are some exceptions of course. This is because the plenum volume is cut in half by the divider, so each cylinder only has half of the total plenum volume and carb CFM to draw thru. Likewise a carburetor with vacuum secondaries will only open the secondaries enough to feed the engine what it needs. Consequently, on a street driven vehicle a split plenum intake with a vacuum secondary carb is the way to go. The vacuum signal stays high for good throttle response at low and mid range rpms.
Fuel mileage is good.
Low rpm throttle response is decreased, but high rpm breathing is improved because of an increase in available manifold plenum volume to each engine cylinder. Consequently, open plenum intakes are a little more sensitive to the CFM size of the carb. If you are drag racing, most folks are willing to sacrifice some low end power for high rpm horsepower. Fuel mileage isn't a concern and the engine spends most of it's time at full throttle. Once you know the correct stock jetting for your particular Holley carb, you can determine whether you live or race at an altitude above sea level.