Aryl halides are generally less reactive than alkyl halides. This is because the carbon-halogen bond in an aryl halide is stronger than the carbon-halogen bond in an alkyl halide. The reason for this difference in bond strength is that the carbon-carbon bonds in an aryl ring are shorter and stronger than the carbon-carbon bonds in an alkyl chain. This makes the carbon-halogen bond in an aryl halide more difficult to break.

In addition, the resonance stabilization of the aryl halide also contributes to its lower reactivity. Resonance stabilization is the delocalization of electrons within a molecule. This delocalization of electrons makes the molecule more stable and less reactive. In the case of an aryl halide, the electrons in the carbon-halogen bond can delocalize into the aryl ring. This delocalization of electrons helps to stabilize the molecule and makes it less reactive.

As a result of these factors, aryl halides are generally less reactive than alkyl halides.