Kinda of a wash cause you will to be in GVA the night before so either way you are getting a hotel. Both will get you there without problems but overall the train is more reliable. If I were making the trip and depending on where I was coming I would probably take the train the day before spend the day (24 hours) in GVA. Trains in Switzerland are quite scenic, some have internet. But 7 hours is a bit long. If pressed for time take the plane.