I think Mesa's performance (both reliability as well as service) has gone up since UA dropped the CRJ-200 flying from them a year ago. The 700's they only fly now are newer than their older 200's and are more reliable. The downsize in their flying has put a renewed emphasis on trying to provide good service as well, as they are batteling to stay alive, and their employees know it. This has shown itself in their work.

Shuttle has the best planes with the ER7.

Trying to avoid a lack of E+ is easy. It isn't just XE that doesn't have it, but any plane, including the CR2 of any other operator, with 50 or fewer seats or a single cabin as well, is lacking E+.

I would rank the planes (and most here would agree) in this order: ER7 > CR7 > E145 > CR2. Some may flip flop the 2 smaller around, as the E145 has poor bin space, but it has the "single A" seat as well as is less likely to have a weight restriction than a CR2. On the other hand, XE has not been as reliable with crew availability the last month or so as the other carriers, at least from my point of view, which does tarnish the ER145's performance, but this is IMHO a temporary thing due to growing too fast in the system.