If you are a GP strictly treating pediatric patients then there is definitely a pay difference. The peds dentist will have higher reimbursement. They are also light years ahead as far as training and capability.
As far as pay, I am a GP and I can do alot. I think I make pretty good money and I just make more every year. My range of procedures is wider. Endo/bu/crown, surgical extractions with grafting and membrane, etc are all profitable. But that range and volume of procedures as compared to a pediatric dentist is what needs to be considered when comparing Pay.
Personally I do see kids and I love it, but I generally don’t go younger than 5. If it’s a straightforward case that’s fine, but I have told many parents that moving forward they should see a pediatric dentist and educated them as to why. So if you wanted to see a strictly pediatric patient population then yes, the residency is absolutely worth it and will have a great ROI.