For us local's choice, you only take the flight in one of the fowling situation:
1. need to be there very early, flight could get you there around 10am, first train arrive after 12
2. need to leave really late, last flight is later than last train
3. company policy or for mileage.

Time wise, there will be about the same. So for leisure travelling mid day, either choice is fine. Train will be better if you've got kids, they could be free depending on age to start with, secondly, there are space for them to run around.

Experience wise, train is good as you could take flights anywhere else, but only china's got the most advance bullet train network.

service wise, J or F service between PVG & PEK are far better than any other domestic chinese route.

If you do have big luggage, then i guess fly will be easier as you do not need to carry the luggage through security, down all the stairs, on to the shelf that is not big enough for check in luggage.