Okay but like actually this is the most thoughtful gift IN THE WHOLE WORLD.
It might seem to make more sense to give Ron the precious family heirloom (remember that Molly’s brother Fabian died in the First Wizarding War; Molly has held onto his watch out of sentimentality since then). But Ron is the sixth son in his (canonically financially-struggling) family. He’s been forced into hand-me-downs his whole life. If he’d gotten the watch with a dent in the back, he wouldn’t have appreciated it; he’d only have seen the flaw. And if his mum bought Harry a new watch instead of getting Ron one, Ron would have resented that. A new watch was a worthwhile expense to get Ron a rare taste of the luxury and individual attention he has always craved.
Harry, though. Harry has money; Harry has new things. What Harry does not have is family. Harry is an orphan. Other than one photo album and the invisibility cloak, he doesn’t have anything that came with family history attached. What Molly does here is give him that; she makes him part of the family, symbolically, by giving him an emotionally significant if physically imperfect item. She gives him love in a tangible form.
This is why I will fight anyone who insults the Weasleys.