I always tell people that it depends on several things:
1) If this is your first trip or not. If it is, you won't be spending as much time in the parks with deluxe dining. If you've done all the parks before at least once, It would be okay.
2) If you have your own car. If you get deluxe dining, you probably will be dining at quite a few resort restaurants. It's much harder getting to and from the resorts from your resort with disney transportation than if you could drive yourself.
3) Picky eaters. If you have people in your party that don't eat much or are very picky, I would do the regular dining plan so that you wouldn't be wasting your hard earned dollars on food that will be thrown away.
4) Whether or not you eat at TS locations. If you eat mostly fast food or counter service or only order 1 appetizer, share an entree, etc. your not going to get your value.
5) Small children. If you get the deluxe, you'll have to eat at least a few very late dinners. If you eat earlier, you'll probably be still full from lunch so if you have small children who normally go to bed early, this probably won't work. The only thing you can do is eat a breakfast, then skip lunch and do a signature meal for dinner around 6 or 7pm which is still a decent time for toddlers to be eating. You could do snacks for lunch if anyone is hungry.
After considering all this, you can decide whether or not you want to upgrade to deluxe.