Hi
Do you still need an answer for that? In my opinion and as a Swiss, I'd say that it doesn't matter whether you stay in the city or near the airport. It takes only about ten minutes from the airport to the middle of the city by train and trains run frequently, I'd say about every 10 minutes. One "specialty" of Switzerland is that with your ticket, you can take every train, which means you can take the S-trains or the IC/IR/EC-trains and you don't have to pay extra or make a reservation for them.

On a saturday morning, you can take the S-train which leaves Zurich main station at 5.02 and arrives at the airport 5.14. That should leave sufficient time.