From where I sit anecdotally, SWA appears to have the most lax mil leave stance/scrutiny in practice, of all the a-world dudes I've work/worked with/for. And leading 2nd place (AA) in that specific race by a large margin too, nevermind the rest of the peloton trailing rather far behind by comparison. To pick an analogy for those of us not making big airline money: if SWA was a returns/customer service desk, they'd be the Walmart of returns desks.
If MLOA maxi-flex (an ART pun, very much intended) was my primary angle in (junior) vocational life, SW would be my #1 choice hands down. It's a good airline to be a dual-status kernel/F-teener.