Alfalfa is a grass with a higher protein content and because it is the favored animal food is usually more expensive than other grasses used for hay. I'd opt for the least expensive.

Alfalfa may have a higher protein content but this could depend on several factors and may not always be true.

I've never heard anyone around here call alfalfa a grass. It's always been referred to as a legume and is often used in a crop rotation for its nitrogen fixing capability.

Lloyd

Alfalfa is a legume, a member of the Pea family that evolved eons ago in central Asia from grasses growing there.