Can't speak about the others, but Sun Country is a real airline with real schedules. I spent a year there and there are way worse places to be based on what I've heard.

That said, it's not a place to think you'll just skate through training. It's a tough training program with high expectations.

But there are two things to note: Pay isn't great by a long shot. It was a huge pay cut for me coming from the left seat of a CRJ. Be ready for that. Also, move to MSP if you go there and aren't from there. It's not a commuter-friendly place. That's not intentional but it's not their business model. Living in domicile and working for SY isn't a bad gig but I can't really imagine commuting there as you'll be on RSV doing a lot of day trips and some multi-day trips.

I'd be more inclined to go to one of the more established regionals though and looking at one with a flow to their major and good movement on the seniority list.

Of the ones listed, SY is the only place to consider a "Career" because QOL can be pretty decent living in MSP. The other places tend to be places you end up at and can't ever leave. SY is generally respected throughout the industry.