My original comments regarding the alternatives from East Herts, Essex, Suffolk etc stand.
On the above basis of waiting, transit time through (a much larger and busier) airport etc., STN doesn't have that much edge in the comparison. From personal experience, it can still take 40 minutes to get from plane to train (without waiting for baggage).
STN for example may be quicker by train from Liverpool Street, but it's Hades when you get there.
SEN would still be preferable for many, given the choice.