"All regionals suck equally" was the advice I got when looking, and I certainly believe it. My advice, pick the one that will cause you the least ass pain. If you're lucky enough to live where there's a base for one or more regionals, stick with those. If you're going to commute no matter who you fly for, find the most pain-free commute you can*, then stick with those carriers. Don't be bought off with snake-oil ("flow" programs)--your goal is NOT to be around long enough to ever be eligible for those.
Also: I wouldn't rely (i.e., wait) on a regional job to get the ATP--get that on your own and apply directly to major/legacy carriers. If you're starting with Envoy (or whomever) in the next couple of weeks, that ship may have already sailed; if you're still active duty and talking several months or more down the road, put that time to use for yourself--unlike money, you can never get that back!--and get your apps in. I was lucky to bypass the regionals altogether (I'd applied in order to get 121 time & stay current; I got hired by a major before my regional class date arrived)... but, I had my ATP in-hand. The time/money you spend on the ATP (time is small; money, less small, but still insignificant when viewed as part of the big picture) will be MORE than recouped if you get hired even a month sooner at your "target" legacy airline....
Good luck!
* I recently saw CommutAir (EWR & IAD bases, I think) has some sort of paid-commuting (I assume that means postive space & a hotel room) program. I know NOTHING about the company, so I am NOT making any sort of recommendation for/against; just passing some info you may find helpful.