Protein is always gonna be a constant debate, and one that I even had to look into and research before making my decision.
I actually just posted this on another thread so I'll just copy/paste:
High protein causing problems is a myth. If the protein is coming from GOOD sources, (i.e. meat) then it's not a problem. If the high protein is coming from grains or vegetables mainly, then it could cause issues because the liver has to overwork to process those kind of proteins. High protein is only an issue if your dog already has liver problems, but even so, some people feed their liver comprised dogs raw food with no problems (I'm not advising this, just saying).
Alot of puppy foods even have 30%+ protein (such as Royal Canin Mini 33). Dogs are carnivores and their bodies are designed to eat meat. Domestic dogs are taxonomically the same species, and physiologically and anatomically the same and actually share 99.8% of the same DNA as wolves. Size and appearance are in the less than .2% differences.
Some dogs don't do well on high protein for one reason or the other but I really believe alot of peoples issues are over-feeding. With a higher protein, more calorie food, it's sooo easy to overfeed. If your dogs are not active, simply feed less. High protein is not bad for lazy dogs, carbs are. Jackson is 16lbs and eats 1/2 cup a day of Acana. Ultimately, though, I think it's what works best for you and your dog. I've done alot of research and have finally settled that this works best for Jackson! I will always recommend grain-free higher-ish protein content foods over grain filled low protein foods but that's just me, I'm no expert or qualified in any way. Through my research, I've determined this works best for us!
Here is another great post from another YT user:
http://www.yorkietalk.com/forums/3163277-post8.html
Acana Grasslands has 33% protein and 17% fat. I also feed Go! Endurance which has 34% protein and 16% fat. For reference, a 50lb dog should be fed 1.75 - 2 cups of Go Endurance which has 470 kcal/cup.