Easier tuning, thats about it though... If you are afraid of tuning dual carbs, and want the look of the 2-1 intake, then go for it,
Its not the perfect way to setup a bike, since no two cylinders are exactly the same inside and engine, and with 2 carbs you can really dial it in and sync the carbs together. All the 2-1 intakes I've been around (aftermarket mind you) have had 1 lean cylinder or 1 rich cylinder.