A dog or any other creature over a kid, hands down. Animals are pretty self-explanatory whereas a parent may want a different thing for their kid. i.e. favorite toy, snack, etc. Animals will love you no matter what; kids can have temper tantrums over the smallest of things.
I have looked after both and admit that given the choice between babysitting a dog or a child, I would choose the dog. I find with kids, when they are not your own they tend to be a little bit more to handle.
Dogs on the other hand tend to do their own thing when you are looking after them.
I've known both needy kids and needy dogs. I think I'll take the kid if it's only for an hour or two. I'm very creative and I come up with a lot of fun activities to do to keep us busy.