Always take the first class available. Classes get canceled and airlines hire till they furlough. That being said, never postpone a class date. Mesaba has been operating the Saab for a very long time, given the choice I would take training with them (I work for Colgan on the Saab, not saying anything bad about the people we have in training, just saying that they have had the airplane a lot longer than we have and they do a great job both with the Saab and training). Seat lock for new hires is only one year not two so equipment and base will only be as temporary as a year if you want to switch.
There are plenty of people in this business that will try to get you down. Only do this if you truly enjoy it, roll with the punches and have fun.