All 3 of my boys had them since both my husband & I have small jaws.
Pros: They are made to expand the width and length of the jaws. The palate is softer at younger ages and will stretch/expand better at this age according to my dentist and the ortodontist that did their work. Worked with a woman years ago who had to have her upper palate cut(yes sawed apart) in a cross to expand hers to straighten her teeth at 28 years old.
Then all 3 of my kids had the braces.
Cons: It IS painful to the kid. You are altering their mouth. If they are permanent, YOU have to help them be responsible for the cleaning out from under them (we used a waterpik.) If they are removable, they can be left behind (ours was at a restaurant in a napkin, thankfully remembered and searched for by the staff before being completely trashed and driving home 400 miles.)
Would I do it over again versus the teeth pulling. Yes, but I would probably also have a couple of teeth pulled.
I had 5 teeth pulled as an early teen to "allow my teeth to move around & straighten themselves out" It was quite tramatic for me, but that was the way it was back then. AND, No that did not happen, my teeth are still crooked.
Except for wisdom teeth, my two older boys have all of their teeth. My youngest however ended up having 9 teeth pulled. 4 impacted wisdom, 4 impacted 12 yr molars and an extra molar that was also under the gum line.
I don't know if this helps, but it is my experience.
Happy Day,
Susan