If you want ORD or LGA out of training it's nearly guaranteed that you'll get one or the other. I'm just finishing training for the ERJ and my entire class got LGA, the class before us got mostly ORD. Everyone in my class who bid for ORD after being awarded LGA got it, including myself. I don't know what the CRJ side looks like, but for ERJ you're asking for the 2 bases everyone generally gets forced into.