Forget which is just better, because that is crystal clear, but lets get back to the "much". Here's the list of players that have come up and stuck with their team since 2005, ie the "young" group, for each team.
Yankees: Cano, Gardner, Hughes, Joba, Robertson, Albaladejo, Aceves
Sox: Lester, Pedroia, Papelbon, Buchholz, Ellsbury, Lowrie, Kalish (and Youkilis came up in 2004)
Yaz's point is spot on. There's value in the Yankee group, but I take the Sox group hands down every time.