Should i start feeding my cat food formulated for senior cats?

Hello, I have a 7 year old, neutered male cat. Should I start feeding him senior formulated cat food? I also have a 4 year old female. She would be too young to eat senior food. I free feed them by putting their daily amount of food in their bowls and leaving it out all day. So, would it make a difference if I feed him senior food? He will probably snack on her food, and she on his. Thank you.