I don't disagree with bigchief, but I've found the opposite, a lot think bigger is better and put large carbs, big camshafts and big honking intakes on their engines thinking they will make monster power as a result. Not always.
While I had mine on the dyno, we took my 800 eps off and installed a 750 holley. I got more horsepower with the 750. I wasn't about to buy a new carb. I had to lean mine by changing needles and jets to get the highest power. It may not have been the rated flow of the carb but it's efficiency, I don't know.
An engine will only pump so much air depending on its volumetric efficiency. Fuel flow in pounds per hour, mass air flow, volume of airflow at standard day, air temp, air density, etc all affect the engine's performance and carb size requirement. There are many formulas to determine volumetric efficiency, mass airflow, PPH of fuel flow, SCFM air flow and on and on. At 100% volumetric efficiency on a standard day my engine should use 671 cfm of air at max power rpm and 644 cfm of air at tax torque rpm. My engine reached it's max power level at 5000 RPM and it's peak torque at 4800 rpm.
SCFM at 100% VE=displacement X rpm/4256=464X5000/3456=671.2964
Now not very many naturally aspirated engines achieve 100% volumetric efficiency although some go slightly above at certain rpm during the dyno runs.
That doesn't mean I should put on a smaller carb, just because a carb is stated to be 800 or 1000 cfm rated doesn't mean one will be using 100% of the carbs rated flow. You have a large carb and only draw what you need but you can't draw what you need if the carb is too small.
I think one has a more efficient system if he or she uses a carb just slightly higher flow rated than the engine requiers.