I am not sure who would eat better... consider:

- the variety of foods available today is far greater, especially in winter - Spices available 1000 years ago were quite limited, today any supermarket will have 100 varieties from all around the world for like $2/satchel - refrigeration allows safe storage of food - Things like ice cream, chocolate, popcorn etc etc just did not exist.

So I think a "peasant" today CAN eat tastier and healthier food than kings of 1000 years ago... whether or not they choose to is another matter.

And same but differently I doubt a king of today eats as well as a peasant of a thousand years ago - aside from famine times. Today we all eat just a few plant and (for most) animal species. This is bad for the gut microbiome, health and our enjoyment of life in general - and its prob true for even the most wealthy.