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There's nothing like being able to tune each cylinder individually.  Nothing to be afraid of.  They just tune and run better.

Think of the firing order - 1432, that's RLLR (Right, Left, Left, Right), or reordered, 4321 that's LLRR.  The first puff through the carb gets the fuel/air mixture going and the second doesn't have to start flowing from a dead start.  The first puff through the carb will not be the same as the second.  Also examine how the throttle plates open:  single throats /  / vs. \  / on dual throat carbs. Since both carbs are the same, both rotate the same direction.  This is true for both single and dual throat carbs however single throats are both mounted with the float bowls toward the front of the car whereas the dual throats turn one around causing both throttle plates to direct the incoming charge toward the intake valves.  For single throats this makes them different not only from first to second impulse, but left to right too.  This makes the mixture different for all four cylinders.  The differences are slight but can be seen on the spark plugs.

Another thing not mentioned yet is that IDA, IDF, DCNF and DRLA (carbs with bearings) all have emultion tubes, air corrector jets, squirter jets, secondary vents, changeable vents and other things that make them much more tunable and generally better at metering fuel...for better or worse.  They are harder to understand but stay tuned as well as any other carb.  Generally, you are doing the same thing on all four barrels the settings are the same on all.  Single throat carbs never really get there, just close.

Most dual throat carbs also have ball bearing supported throttle shafts as opposed to steel on zink common to most single throat carbs.  The ball bearings provide for smoother, more accurate throttle positioning as well as reduced wear on the throttle bode, the softer of the two metals.  When the throttle body becomes worn. the throttke shafe and plates can move around with undesirable results like uneven positioning, sticking and vacuum leaks to name a few.

If you've ever run dual 2 barrels (not progressives) you surely understand and would never go back.