XJT. Their IAH base is not going anywhere and is actually growing. CRJ's, -145s and -175s. So I would think you should be able to get it within a year, as pointed out by others.
Mesa... who knows. IAH base may still be there in a year... maybe not.
Also, a bunch of former ExpressJet pilots at Kalitta and currently there is a shortened interview for XJT pilots. So if that is your goal it may help.