One TiW card is good for up to 10 people. I believe just a few holidays the card is not good - Mothers Day, Easter Sunday, Independence Day, Thanksgiving Day, Christmas Eve, Christmas Day, New Year's Eve, and New Year's Day.
We're a TiW family most of the time. We often like appetizers, either in addition to or as the main course. You generally can't do that on the DDP, unless you only eat at a select few restaurants with limited prix fixe menus or get the DxDDP. We also aren't big into desserts immediately after our meal. So in general TiW works best for us. Don't forget that TiW is also good at some counter service restaurants - the main ones in AK (Flame Tree, Pizzafari, Restaurantosaurus...), the value resort food courts, and Sassagoula Floatworks at POFQ. The 20% savings at each really does adds up!