It's perhaps my custom that is being tussled over by BHX and BRS. I live in an affluent part of the Cotswolds between Cirencester and Cheltenham. This is how it looks from here:
BRS 1 hour 13 minutes, 52 miles
BHX 1h 13m, 65m
LHR 1h 22m, 82m
CWL 1h 42m, 89m
EMA 1h 46m, 95m
LTN 1h 54m, 96m
EXT 1h 55m, 118m
LGW 2h 2m, 123m
MAN 2h 18m, 136m
LPL 2h 33m 151m
I wouldn't dream of using public transport (half a mile walk to bus stop, two buses to Cheltenham station, lugging suitcases!)
Of the above, I have used BRS, BHX and LTN most often, plus EMA, LGW, LHR and LPL on occasions.
It's about flight destination, timings, airport accessibility and airport parking, balanced against cost.