There's a very basic article on the quality of rabbit pellets here
http://www.thenaturetrail.com/rabbit-health-feeding/pellet-formula-nutrition/ and a link to an article that breaks down possible ingredients. I would prefer a fixed ingredient pellet like manna pro and then a fixed analysis pellet like purina. I think it's more important to have a predictable list of ingredients than meeting certain nutrient profiles and I do think different proteins, carbs, or fibers do make a difference instead of just matching the numbers. I also want molasses low in the list.
I wouldn't touch the fixed cost pellets but they are pretty easy to pick out. Things like country lane that just reads as a list of vague byproducts with no named ingredient. I believe the first 2 ingredients are roughage products and grain byproducts which means they can stick whatever the heck they want in there that keeps a batch low cost.
For chins specifically I've read 16-20% protein but I think this might be a little high for pet chins. They do likely require a higher protein on average than a rabbit or guinea pig because of their coats but 20% might be too much for a chin that isn't producing offspring, trying to grow a good coat quickly for pelting, and has limited stress in it's life. Too much protein does stress the organs some to filter out and causes more concentrated urine. You want around 30% fiber overall but that includes hay so your pellet can be lower like around 20%. Feeding more than one type of hay is suggested.
