I picked medium, but really that's from the assumption of having experience with more forgiving fish, first. Jumping into discus as a first tank, I'd say hard, but reserve "very hard" for reefs or fish with special feeding requirements.
You need to do a bit extra for them over regular fish, and they need pristine water quality, but that's highly recommended for any fish anyway. They don't need any special feeding or particularly complex setup, though.