I dunno, OP. I had cats growing up--one was killed by a dog while on our screened in porch, where they hung out a lot of the time (I think there was a hole or something that a dog got through). It was a horrible situation.
Now, I have a very large, strong dog, and we have a neighbor who sometimes lets their cat out. I've only seen anyone out with the cat once. The cat roams the lawn and driveway, and appears to be unafraid of my dog. My dog has only seen the cat a couple of times, but it's all I can do to restrain him while he flips out and tries to lunge toward the cat.
If I ever have a cat again, I would only consider letting it out if we have a secure and fenced in backyard.