My two cents: right now it's a pilots market. I'd take any job that is better than your current one, especially if you would be happy there long term. You can always move up again, if you are given the opportunity. There are no guarantees in this business, so always try to position yourself as best you can before the music stops. I think being more well rounded will serve you better in an interview down the road.
Just think of how many regional pilots have apps in at the legacies, you need to set yourself apart from the pack in order to get a call. I think those who tell you to stay at a regional because legacy airlines prefer it are leading you astray. You have 121 time, pic and LCA time are a better addition to your resume than thousands more hours of the same thing you already have.
Now, if you have a flow up to American, forget what I just said and apply to the other legacies and wait for your number at AA.