From the prices you were quoted it, it sounds like you were offered the Plus level vouchers, probably because you have chosen to stay at Hotel New York. As far as I know all the buffets in the park, Restaurant des Stars in the studios and La Grange in Disney village are all covered by the standard value half board vouchers. So if you ate at these with the plus vouchers you would be losing out so probably not worth it. The buffets in the restaurants at The New York, Sequoia and Newport Hotels are the only I can think of where it would be worth using Plus vouchers as I think you get a free drink included.
Wondering if its worth going half board at Disneyland Paris. I struggle to eat three courses so would more likely go for the buffet rather than the set menu, DS can be picky so would do the same. We have been quoted £24 per adult and £11 per child for half board vouchers so are we better getting the vouchers or paying on the day?