It's the same thing — no difference. For regular search queries it's the same BTW.
Conceptually GET might make more sense, since you are just fetching data and it's an idempotent command. However, GET doesn't have a body and some clients (like browser plugins) might simply not send the body if you are doing a GET. So POST is an alternative, which has a body, but is maybe not the right HTTP verb for fetching data.
Generally we are trying to stick to REST conventions where possible, but we will also pick pragmatic alternatives if required.