I would avoid Mesa. Work rules are near the bottom of the regionals. Many pilots I fly with, jumped ship from Mesa after a year or so, and went to another regional.

Envoy, ExpressJet, Skywest are all top-tier regionals (but that is not really saying much!). They all have their pluses/minuses.

When joining the regionals, definitely do some research into their particular work rules. Quality of life can vary widely.