Hi Alex
Birmingham and Glasgow are both pretty lively cities. You are right Glasgow probably has a better music scene but the Birmingham one is pretty good also. Birmingham has better weather and its easy to visit lots of places as it is right in the middle of England. Glasgow is probably a cooler (as in style) place with great mountains not far away.
Strathclyde and Aston are both city universities, modern buildings close to the city centre. Birmingham is on a super-beautiful campus in the suburbs. If you picture yourself studying outdoors, under a tree then BU is for you.
As for the marketing courses you have summed it up. All 3 are excellent with their respective strengths. It is not possible to say one is better than the others, its down to individual tastes in terms of course structure.