Ben:
I had two pit bulls. Both females and fabulous pets. Great athletes, loyal, and yes reliable baby sitter and protector. Both enjoyed playing with other dogs, killed multiple rabid raccoons, snakes, snakes, and rats. One of them loved to get one of my horses to chase her around the pasture just for the joy of it. The only time they would get into a fight with another dog was when a larger dog would start something. Neither were aggressive with a smaller dog.
Unfortunately, the macho folks have abused and nearly ruined this breed (ally fights, scatter breeding, etc.)

When they do break bad they are horrific due to their strength and violent shaking. They do not go for the throat like a doberman but grab any part and shake. My council is to neuter and then properly socialize the pup. While lots of fun for both of you, do not play tug of war as it teaches them aggressive behavior.
I wish you the same joy with you new family member as we had with ours.
CB