Changing Cat Food

We have a 14 year old cat who had a UTI and stones twice when he was about ages 2 and 4, if I remember correctly. We've been feeding him the Purina One food for a healthy urinary tract since then. The last time I went to buy food, the store was out of that kind. I bought some Cat Chow for Indoor cats. Both of the cats seem to really love this food. The best part is that they have not vomited their food since they started eating this. With the other food, they were vomiting nearly every day. I was told that's normal so I didn't worry about it. I'm wondering if I should just keep buying this food even though it's not a specific kind for a healthy urinary tract?