Both companies make and have made money consistently for a number of quarters, if not years/decade. They are relatively conservative as far as growth, maybe not so much as SWA, but their business model works. Based on past comparisons, it is unlikely that they will morph into the next major airline. However, they are both ripe for buyout/merger.
Pick either. Your future would be relatively secure (for an airline, anyway). If you've learned anything from these threads, never choose a long term place of employment based on bases/pay rates in 15 years/etc.