I think Silver Airways, Spirit, and Allegiant are best for getting all short trips, anywhere else it will take seniority. You might want to prioritize your end goal, such as which airline will get you the earliest class date, get you through training fastest, and get you flight time fastest so you can move onto your goal airline before the hiring wave ends. It’s possible a year or two at a regional would get you to Spirit or Allegiant. You might check whether Allegiant or Spirit share junior bases with any regional airlines so you can plan on fewer moves.