Before you consider changing, I think you should appeal to the insurance company to continue to cover the Concerta at the old rate.  Asking you to change is not medically prudent if your son is doing well on Concerta.  Although Concerta and methylphenidate are the same active ingredient, they get to your brain at completely different rates in the two different preparations. 

I saw this happen several years ago when BC/BS in NY added Conceta to their formulary. At that time, they bumped Adderall XR and suggested that people change to Concerta.  Now they're suggesting a change in the opposite direction just because they got a better deal from one company than from another.

I don't think we should let them do that to us again without a fight.