A couple of peeps have actually chosen Atlas over B6 while waiting for class dates. You may not be aware, but commuting and sitting rsv is miserable. Atlas guys have a lot to deal with and negotiations may get nasty, but they are able to avoid jump seats and crashpads by having a plane ticket and a hotel room. Just ask any of your commuters who were formerly at Comair how much they enjoy their commute.
It's a personal choice I guess and from what I see here, jetBlue ain't the best place to be. There are a healthy amount of Atlas FO's gaining class dates at Purple and Brown so it can't be that bad of a stepping stone.