German Shepard. I had one growing up, and I loved her. Most German Shepard's are kind hearted, and loyal. They are playful, and very protective. They are easy to train, and they mind well.
That being said, I have never owned a rottweiler. I have just seen them in passing. In all honesty, the ones that I have seen. Didn't make a big enough impression for me to want to get one. I can't judge yay or nay about them.