I have 4 indoor cats. I grew up with indoor/outside cats and have always pleaded with my parents to keep them indoor only cuz it's safer.
As I grew up, I have seen my old indoor/outdoor cats getting in fights so we'd have to take them to the vet to have the wounds cleaned (some would get infected so that didn't help either). I always worried about people stealing the cats, dogs catching the cats, etc so i never had peace of mind when I had indoor/outdoor cats.
One cat almost had to be put to sleep by the pound. My parents and I had to fight real hard to get her back-she had caught a bat. That's a LONG story which I won't get into but the point is that cats are exposed to many dangers outside.
My mom often complains about finding dead birds and mouses in the house and I keep telling her that I have had NO problems with that with my indoor cats!
Now, when with my indoor cats ONLY, I have almost NO worries cuz I KNOW they are inside SAFE from harm.
I STRONGLY recommend keeping ur cats indoor. Be sure to have plenty of toys, cat trees, give them attention and they will be happy!