u/Tarn-ished

Hi, I have 2 cats(kittens?) Who are coming up on their birthday in a month and some change. I was advised by the shelter to keep them on kitten food until then. The food they ate there and have been eating since is Purina Pro plan. My question is since they will be upgrading to full-on cat food is there a specific way to choose their new food? Do I stick with the same brand or could I entertain store brands that are offered by my job for instance that are a fair bit cheaper? I'm not sure what to look out for in terms of comparing and needs in a food but don't want to risk compromising on their health a bunch