The Tribute feed sounds better because the tag lists actual ingredients and throws around terms such as "high fat," "calm performer," etc. But it is still just a sweet feed according to the tag.
From what I can see on the nutritional analysis, both feeds are actually pretty darn similar- the same amount of protein, similar amounts of fat, fiber, etc.
But I can understand why you are upset. I would be too. I would want my horse to have the better feed if I was paying the same amount of board as others who were on the "better" feed.
But looking at the analysis, at least the first few ingredients, they seem pretty similar. The "good" one is a sweet feed according to the tag. I assume the cheaper one is too?
I personally would talk to the BO and see if you can get your horses on the "better" feed.
Incidentally, Purina, whom I've used and consider a good feed, lists "grain by products" on their lists of ingredients too. They say it is so they can be flexible with ingredients to get the appropriate nutritional content in each batch of feed. Because not all ingredients will have the same nutrients from batch to batch or something like that. (Yeah, I've been to a couple of Purina horse owner's workshops, ha ha!)