How to choose the most suitable Aer backend simulators in qiskit?

I am going through the qiskit documentation of simulators. I have learned that there are many types of simulators, and the main simulator backend of the Aer provider is the AerSimulator backend. However, in many other tutorials, statevector_simulator and qasm_simulator are used quite often. Can anyone explain what is the major differences of all these backends, and how to choose the most suitable one depending on different needs?

They are mostly differed by simulation methods and maximum qubits. QasmSimulator is the closest implementation to a real quantum computer where all the readouts are in binary strings. I usually test all my code in this simulator and simply change the backend to a real quantum device. In StatevectorSimulator, you can readout the quantum state in vector form. UnitarySimulator allows you to print out the matrix form of a unitary quantum operation.

More details coming later...