The main benefit of quantum computers is that they're (in principle) very precisely controllable quantum systems. In a sense, if you do a "quantum simulation",

The main benefit of quantum computers is that they're (in principle) very precisely controllable quantum systems. In a sense, if you do a "quantum simulation", it's actually physically real since you are actually working with the same quantum states and interactions you would have in the "real thing". Apart from some strange cases (usually using quantum fourier transform, such as prime number factorisation) they are not good replacements for classical computers at all.