You bid the run along with the city it's based in. Each run has designated aircraft, it could be 1 or all three. Typically a run will be one aircraft or two, unless you are a reserve captain then most times you will be trained in all three. You get 1 base move per year within the same equipment and unlimited laterals within base. I believe if you change the grouping of aircraft you are trained in, then you have to sign a new 1 year contract. The Navajo and C208 are definitely more comfortable but most pilots are more concerned with where they are living. But a year goes by fast and if you are willing to move the upgrade will come fast too. Finally if you plan on staying for the lear it's pretty short too. All the tall guys end up removing the back cushion and some remove the seat cushion too.

Good Luck!