If that is your choice, I'd say go to C5.

I considered Mesa briefly before going to C5 because I wanted to continue flying the 175 after Republic and Mesa was the only other carrier within reasonable commuting distance that had that option. But at that time I heard stories of 6+ month training delays and bad training experiences on the 175, and after having a bad experience at Republic I was in no mood for a repeat. At the end of the day I concluded that I'd get the same turbojet experience at C5 flying the 145 and get my preferred EWR base option pretty much guaranteed so it was a no-brainer. Remember: if the only choice is commute vs. live in base, it's live-in-base ALWAYS.

Mesa also has a stigma in this industry, deserved or not. That is not to slight the crews or suggest that Mesa guys can't move on (all but the worst offenders can and do) but I think it's fair to say that Mesa will hire almost anyone, whereas C5 has been a bit more selective, even a couple years ago when they were practically begging people to come here, and it's that stigma that may generate increased scrutiny when you try to move on.

C5 is also partially owned by UA, and while that doesn't mean a whole hell of a lot from the perspective of the pilots in the day-to-day, it should mean greater stability over the long haul. UA is the only carrier that still has eight partners. Not sure why that is, but I do see them reducing the number of partners eventually. The new 175 deal with Mesa guarantees they'll be a part of the mix for the next few years, but who knows after that.

In terms of "soft" qualities...one huge perk of C5 is the relatively small size of the company. While we're definitely growing we are still small enough that you'll get to know people, see them on the line frequently, and make friends. As I have worked in predominantly small companies my entire career I consider this a huge perk.

The upside to Mesa, from the little I've deadheaded on them, is that whoever hires the flight attendants defines cute the same way I do. Though I shouldn't have to tell you this means absolutely nothing from a career perspective, the scenery is definitely nicer at Mesa. The mountain views on their predominantly western route structure are also breathtaking.