We’re running a class every two weeks. Class sizes seem to be between 12-20, depending on a number of factors.
I’m not a good source for contract/bidding info, so someone else will have to answer that one.
As for which to choose, really weigh what’s important to you. Is it the base? The equipment? Money/benefits? Culture? QOL? Flow/no-flow? Bragging rights? The main reasons I chose Republic are the Indianapolis base and the E170, but everyone has different priorities.