There are different levels of Purely, IIRC from about 40% to 70% meat. I would opt for the food with the highest declared meat content: most cat foods have a high protein content but this can come from an animal source or cheap fillers such as waste products of the cereal industry. Unscrupulous companies will list a few different grains so that they come further down the ingredients list and meat can come first.
![knackered :tired:](https://www.purrsinourhearts.co.uk/Smileys/purrs smilies/sleepy.gif)
At the end of the day cats are obligate carnivores with no nutritional need for carbohydrates; furthermore protein from animal sources is more bioavailable (better absorbed and utilised).
Sorry Sam but I don't trust Royal Canin as they are one of the only 'premium' brands which don't declare the meat content, and won't disclose if you e-mail either.
![Shy :shy:](https://www.purrsinourhearts.co.uk/Smileys/purrs smilies/shy.gif)
Where money and extreme fussiness is not a concern, my preference is for Orijen, Applaws, Encore, Porta21 (sensible variant) and similar grain-free foods.