The only thing I can add to the above posts, is that you should also consider the fact that the industry is now in a bit of a downturn...so, with that in mind, I would recomend chosing an airline where you can weather the storm, and there by be ok for the next 4 to 6 years.

There's this myth right now among many of the young pilots getting into the industry that as soon as you get your "magic" 1000, you're gone.....not so much, so while upgrade is important; stability, QOL, domiciles, pay rates and soft money, should also be factors in your descision.