Getting from Newcastle to Stansted by rail changing at Peterborough and avoiding London takes 4hrs plus or minus 15 mins depending on the connection. So if you are going to Stansted to fly on from there the plane is much quicker. But if you were wanting to do a journey from the centre of Newcastle to Cambridge there's little or no time to be saved by flying via Stansted. As for price there are plenty of cheap rail seats on the East Coast at present. If you book far enough in advance you can get from Newcastle to Stansted for £16 single, and there are a lot of options for around £60 return. By contrast cheap seats on the Cross Country rail service are like gold dust. So it doesn't surprise me that Easyjet seem happier with the route to Bristol than to Stansted.