The proof in the pudding which passengers (not geography students) care about is accessibiity. Prestwick is as quickly accessible to Glasgow as most other major UK airports are from the city centres after which they are named.
Prestwick is not a bad option for glasgow so I would agree with the name - I seem to remember it was 25-30 mins on the train into central glasgow when I did the run (about 10 years ago). That is less time than stanstead/luton/gatwick and about the same time as Heathrow into central london.
Cheers
Jof
p.s. Glasgow Prestwick Airport is allegedly the only place in the UK where Elvis set foot (I seem to recall a placque in the lounge).