We did the Deluxe Dining plan for quite a while when both kids were under 10. We always had at least 2 sit down meals a day, a lot of character meals, some Signature meals like Cali Grill, Hoop De Doo, etc. Because there's been such a precipitous drop in price between adult and kid, it wound up being to our advantage, even if we had credits left over, and we'd bring home tons of packaged snacks or the nice big bags of Trail Mix.
Past trip, we switched to TiW. One the one hand, there was serious sticker shock when we got the AmEx bill as opposed to paying in advance. On the flip-flop, we just ate what we wanted. There wasn't a mental push to fit a dessert in there. We'd share an appetizer, we'd share a dessert. I don't drink so I didn't have to ask if my wife could have my alcohol and maybe we pay out of pocket for my soda. Servers would, without being asked, just offer to let my older daughter, now 10, order off the kid's menu (including Be Our Guest, they only charged her the kid menu price).
And barring awful service, we'd just put the 20% back on as the tip.
There's a convenience to paying one price and being done with it. But there's also a convenience to knowing you can eat what you want - "I was going to order the filet, but I think now I want the chicken, but then the value of the dining plan goes down oh noes!"
So unless you're in the boat we used to be in - your kids are under 10, you intend to have 2 sit down meals a day and maybe a sitdown on your checkout, you're doing the Signature meals where 2 credits can really work out (like Cali Grill or Jiko or Poly Luau or Hoop-de-Do, as opposed to BoG), you do a lot of buffets/character meals that are prix fixe...AND you plan on the Deluxe Dining Plan...I'd say TIW is your better bet.