Just to point out that for London-Glasgow most people would be taking the Virgin Trains service from Euston which is about an hour quicker than GNER via Edinburgh.

As to which is better, no-one can say which is better without knowing the details of the trip including start / finish points and date(s) & time(s) of travel

Note BTW that an open train ticket (and many semi restricted ones) do allow you to take a different train from that intended so you don't have to worry about meetings finishing early / late