[Help] What food would you reccomend my Senior Lab - Kirkland Mature Dog, or Kirkland Natures Domain Grain Free?

We already supplement with Cosequin DS for joints every day.Currently feeding KS Mature Dog - I wanted to see if you guys think we should stick with that or switch to the grain free Natures Domain line (and obviously continue with the Cosequin joint supplement.)The reason we chose KS Mature is it has a higher rating on dog food advisor.I know very little about this. I need all the advice I can get. via /r/dogs http://ift.tt/2s6KBUK