I moved here from Europe. There they're just starting with "industrial" hay production, like hay as a single species crop. They do have higher protein yield grasses for milk production, but usually horse hay is considered multi- species natural, minimally fertilized forage.
Now if you think about horses being highly selective grazers, offering only one species of grass gets boring. Not only that, also lack of certain nutrients on one end, and over-providing others comes with it.
IMO, getting as many different kinds as possible and mixing it together is the way to go. I've been doing that, mixing timothy/ orchard, oathay and alfalfa.
I've found through observation, that my horses nibble a bit alfalfa, then off they go to the oathay, then it's more alfalfa, then it's o/t time, all day long.
So, if you have the possibility to mix and match, by all means, go for it.
If you are worrying about metabolic problems, the majority of the ration should be warm season grasses, like the Bermuda's, since they are generally lower in NSC's.
Never fed peanut hay, but it's a legume, so it's most likely higher in energy and protein.
Sorry to not be of more help