We feed both in wet & dry. You can check more info out at: http://www.nutroproducts.com/ The Indoor is suppose to help with less shedding, hairballs & less stinky bathroom issues. I'm happy with Nutro Indoor & Natural, my cats like it too . Their coats are silky, shiney & soft. I'm sure someone else will have other
Indoor adult has 33 protein 14 fat and 150mg/kg of lcarnitine for fat metabilism and lean muscle mass... It is designed for less active cats ... Also it has soy protein and extra D and E to help with bone health and extra coat care
reg has 33 protein and 19 fat .... I use the reg kitten for my girl who turned out to have a soy allergy
I used to have Kitters on the indoor but one day when Petsmart was out of Indoor I got her the other. She seemed to actually like it better and she had less hairballs. It'll also depend on your cats reaction to the difference. Good luck with making the choice to stay or change.
What ever the difference is, I can tell you my cats noticed. They have eaten Nutro Natural since they were babies & I tried to switch them to the Indoor. They wouldn't touch it. I was amazed that they even knew the differnce.