I can’t really speak much about Ritalin as I am not familiar with it but I am familiar with Vyvanse, it has worked very well for my daughter with only a couple of side effects, her appetite almost disappeared in the beginning but that did improve a little over time, she still eats far less than she used to. The only other issue we have is sometimes it is difficult to get her to sleep at nights, this is not a regular issue but it does happen from time to time.
Other than that Vyvanse has been great, it controls her symptoms very well without changing her personality at all.
You are correct about it being kind of trial and error in finding the right medication, they don’t all work for everyone. Good luck to you!