Alright well I apologize, I am just annoyed by questions that are answered by a simple google search. But you joined this forum for a reason. Here is your answer. There are different styles of shooting for different competitions. The one handed method is called bullseye shooting where you use one hand and shoot 3 different targets with three different time limits to get the shots off. This is not practical, defensive shooting like you would see in IPSC, IDPA, or TDSA. The 2 handed shooting is more practical, but there is other competitions like PPC where you shoot every possible way using good hand and bad hand so it is useful to practice. Really you should figure out what kind of shooting you wanna do, and practise that style. Just watch some videos of IPSC, and Bullseye shooting to see what I mean. Good Luck.