Me: "Do you require an IFR or VFR clearance?";
You: (Be truthful. It simply isn't my place to suggest.)
It's not a matter of truthfulness.
I might be VFR on a gin clear day wanting to go through a Class D zone.
I have heard some controllers say that they prefer IFR because they can vector me and assign a level, whereas on VFR I am a loose cannon.
I have heard others prefer VFR because they can apply reduced separations.
Presumably it depends on the day and the traffic.
If I am happy with either I am happy to tell the controller so. Nothing to do with truthfulness.