The value of concierge is very subjective. The Wonder & Magic do not have concierge lounges (yet) and as I understand it, the rooms are spread out around the ship. The Dream and Fantasy rooms are on decks 11 & 12 and the lounge is on 12. It really depends if you will utilize the services offered, such as booking a cabana, adult dining, spa treatments, meet & greet tickets, tastings, etc, as well as the lounge. The lounge is wonderful for adults & kids. They offer small bites for breakfast, lunch, and during the evening receptions. There are unlimited soft drinks and bottled water available and during the evening receptions, an open bar. There is also a private sundeck with towels, misters, and sunscreen as well as a private character greeting.
If I could afford it, I would only cruise concierge on the Dream or Fantasy, both adults only and with my children (19 & 12) as we feel the amenities are worth the additional cost for us.