Knowing the closest major airport would help. The sad reality is that like everyone else, barring any need for a specific frequent route, you're likely best off choosing the airline which dominates the closest major airport.
Back in the Virgin America days, I almost exclusively flew SAN-SFO and became Silver even though VX only had a few non-SFO flights out of SAN. WN is the dominant airline here.
Once I stopped needing to go up to SFO frequently, I was worried I'd lose status and it might end up making more sense to fly WN, despite my dislike for both open seating and Terminal 1.
Thankfully that drop-off in SFO travel happened around merger time, and the AS board heard my prayers and there's currently I think 30 destinations on AS from SAN. If not for that miracle, I'd probably be flying WN. If you're not flying the airline often, you're not really using the benefits of status, so what's the point?