In my case depends of the following considerations:
1- are good options to eat in the destination? i.e. I am now in Deauville, and options are quite limited in terms of opening time, supermarkets around, etc.
2 - Fridge in the room - great for keeping yogurts.
3 - price of the breakfast. If I can have a filling breakfast that will keep me fine until dinner (with a snack) I think its worth it in general.

I can show the breakfast in Deauville if anyone is interested, quite good.