Rule #1: Treat airline recruiters like military recruiters. They'll tell you all of the good, and none of the bad. It's their job to get you to sign on the dotted line.
Rule #2: Avoid commuting if at all possible for a regional.
Rule #3: Do not pick an airline based upon what planes they fly. E145, 175, CRJ, no major cares what kind of regional jet you flew.
Rule #4: Look at the referral incentives the airlines are offering their employees. They're basically turning their pilots into paid recruiters. Take what pilots say with a grain of salt for that exact reason.
Rule #5: Go to the place that will get you gone the fastest. Your goal is mainline, not a regional. However, if the music stops, try to be somewhere you can tolerate.
I'm at 9E. It's improved significantly since the BK and merge, but it still is lousy in comparison to any major. All regionals suck compared to the majors. Get in, move out.