Or is there another brand even better? I have a senior house cat.

I don't consider Purina, Iams, Science Diet or Royal Canin to be good foods. I would recommend a grain free food such as Wellness.

good luck!

Iams, Purina, Science Diet, Friskies etc are all rubbish.

Take a look at the labels. The first and primary ingredients should be all named meat sources. No corn, corn gluten, wheat, soy, beet pulp, brewers rice. No by-products, by-product meal, animal digest, or unspecified meats.

Cats are obligate carnivores and the nutrition they require is that which best approximates that found in their natural prey.

Not only should the cat food contain no grains, by-products or mystery meat, it should not be a dry food either. Choose high-quality canned foods such as Wellness, Wellness Core, Merrick's, Natural Balance, Blue Buffalo Wilderness.

Here are some sites about cat nutrition. After you read them you will understand how to choose appropriate cat foods on your own:
http://www.catinfo.org/
http://maxshouse.com/feline_nutrition.ht