This is similar to when my wife and I visit the UK, we usually do a week in the south and a week in Scotland. And we traditionally take the LNER between just because Getting to an airport will be a 45-60 minute cab or train, then dealing with security, baggage, etc, so all in all a 3.5-4 hour journey. London Kings Cross <-> Edinburgh Waverley is a 4-5 hour, usually OK train ride (if the A/C is working), and you get on and have wifi (sometimes), and can pull out your laptop and put it on a REAL table.