Well, I am a dog person. I suppose first and foremost, I'm a dog person because we never had cats around, because my sister has ailurophobia and is deathly afraid of cats. There's no rational reason for it...she just hates them with a passion. And it's just as well since it turned out, as I learned when I was about 16, that I was highly allergic to them. That's gotten better over the years, but I still have to be careful about touching them and then touching my face, etc.
But I like dogs because cats are a little too independent for me. They pretty much do what they want to do, regardless of what YOU want them to do. That makes for some interesting entertainment and interactions, but I don't know if I want that in a pet...I've had too much of that in my previous relationships. LOL