I have not ever had a Barred Rock be aggressive (I suppose it is possible that some bloodlines might be--mine would quat down and let the children pick them up.) If it were me, I would try one of each breed. You have to decide what is right for you. Do you like uniformity (all the same color and/or breed) or do you like to mix it up? I like lots of variation in my flock and egg basket. My best friend only wants to see one flock of a single color foraging across her pasture. Up to you. Have fun!