I also recommend the allaboutdogfood to check ingredients and ratings.
Different dogs respond better to different foods so I would go by the ratings then order small bags to try out for your dog. You will know best (initially anyway) by the output.
When we got our lab puppy we switched to Eden which has fantastic ratings but it gave him dreadful wind and runny poos (whereas a previous posters dog was good on it), we spoke to Eden a few times and they kept recommending preserving
but two large bags later it was still no good.
We then tried Millies Wolfheart Riverside which was a bit better, formed poos but still very soft and still windy. Then we tried Millies Wolfheart Countryside which was perfect for him, with those longed for small firm poos, a pleasure to pickup and no more wind!!!
We think some fish disagrees with him which is why Eden and Millies Riverside didn't work well. He is now 7 and gets various flavours from Millies and they are all great as long as we avoid anything with white fish or trout. He is okay with Millies Salmon 25%-50% mixed in with another variety.
The other good thing with Millies is you can pick a variety suitable to their level of activity as they do various protein and energy levels. Now we know what he likes we order 3 bags at a time (2 normal and one Salmon to mix in), it is a big outlay but is cheaper and they last months between deliveries. They also do lots of natural chew treats, but I found most of them you can get much cheaper elsewhere.