It depends on the quality of protein. However, I wouldn't put much faith in the protein in kibble, because honestly, I fed my dog a 40% protein grain-free kibble for a couple of months. He did appear leaner, but isn't protein there to feed the muscles? He didn't develop muscle mass, which I find pretty odd.
If your dog is active he will do okay on a 38% protein kibble, as long as it's quality protein.