High moisture hay will be somewhat higher in protein, due to handling it at a higher moisture. There is less leaf shatter and loss, particularly in legumes. Two more reasons cows seem to do better on silage: it is more palatable at a higher moisture, and the fermentation process is equivalent to being partially digested for them. The last eight years we had dairy cattle, we fed no dry feed to the lactating cows, only corn silage, haylage, and high moisture corn until it ran out, then dry corn. We fed a total mixed ration and I noticed the cows could eat more pounds dry matter in a day eating fermented feed. That translated into more milk production at a slightly higher cost of making feed. I don't know if the higher intake of feed will pay with beef, or not, but you will love making higher quality feed on a much higher percentage of your crop!