Glasgow has plus and minus points. Long runway, expensive and time restrictions, stunning views and easy access. Full fire cover and air ambulance on site.
LEFT is friendly enough, and very supportive. Subject to a check ride, you can just turn up and fly, within permitted times and they have a good choice of airframes. Glasgow Flying Club I've found to be a bit offy.
Prestwick Flying Club, as a club, is awesome. Just the one aircraft, and a bit under-powered at that, but really nice people, and a smashing friendly atmosphere.
Prestwick Airport is great, two big runways, 24*7 availability and the most obliging ATC staff you could ask for. Full time ATC and Coastguard rescue helicopter on hand 24*7, so it's a warm fuzzy feeling all round.
Prestwick local area, stunning scenery that takes a bit of beating. Submarine hunting or Island Hopping, you choose. Prestwick is getting my money for a mixture of all of tha above.