At SkyWest, the further west you go, generally the more senior the base on the jet. I have heard of some newhires getting COS and DEN though. Keep in mind you could get the Bro which is all west coast (most eastern base is SLC, which tends to go more senior). You'll hold a line quicker on the Brophus than the jet and have a greater likelihood of staying on the west coast. Upgrade is dependent in airframe, slightly longer for the jet as you might expect.