Using dual supplies will allow the output to swing both - and +, almost rail to rail. If the - rail is connected to gnd with a single supply the output will swing from just above 0 to just below + rail. Which you use depends on the application. If you a just amplifying from a circuit with a common ground, then single supply is ok. Or say you want to amplify a sine wave with a centre zero reference, then you must use a dual supply. Doing a search on the net for op amp theory will give you a better understanding.