Will you able to be able to live near where you work in London? In Glasgow, you will almost certainly be able to afford to live in a nice place in the city centre where you can walk to work. People usually underestimate how much effect a long commute will have on their happiness (see e.g. here).

Also, you might consider trying this. If you're still unsure, chances are the expected value of the two options is pretty close, and you shouldn't worry too much about how you make the decision.

Disclaimer: I am in Glasgow, and would like to increase the population of LW-type people looking to make new friends who are here, so I'm probably biased.