Before my nephew was ultimately properly diagnosed, he was on Ritalin and got switched to Concerta. Now his reason was that he would forget to take it once or twice a day, thus the Concerta made it easier for him to remember. But he is much older than your son, why did they say they were switching him?
One problem with this drug is that it causes massive weight loss and insomnia, both of which we have seen in Felipe and so have stopped its use. Ritalin causes a loss of appetite as well, but because it is taken in many doses you can regulate it, but not so with concerta.
Here is good info on it that LDS_forever pointed me to about the weight-loss factor:
https://www.additudemag.com/experts.asp?DEPT_NO=301&SUB_NO=30
As a personal user of Concerta I believe it works amazingly. I had used Concerta for a while, and we switched because coming off my medicine I would be extremely irritable. However, we then realized my new medicine did that as well. We switched to Concerta because it last longer. Also being a user of Ritalin (Using Concerta for school because it lasts around 8 hours I believe, and then coming home to take one dose of a 4 hour Ritalin) I can tell you they do work pretty much the same, except on Concerta like he said it does make it's user have a loss of appetite. However, it's worth it because I'd much rather not be hungry than be unmedicated. It's rather scary because of my unable to focus, and espeacially in school with all the test's the government gives now a days.