Police dogs (patrol & handler protection) in the United States are usually, German Shepherds, and Belgium Malinois, and that's for several reasons. Their bred for INTELIGENCE & TEMPERMENT, character, (yes dogs have character), willingness to learn (train ability), athleticism, dependability, COURAGE, ability to handle stress (mental & physical), and BITE PRESSURE.
I personally learned early in that a huge dog, is not necessary to take a big man into custody. A 60 lb dog is PLENTY, if trained and the dog has the above mentioned traits. The Belgium Malinois fits this bill, but needs a strong handler, as the dog is born in HIGH GEAR. He is an over achiever in the dog world. Not quite as sharp in the mental ability as a German Shepherd (in my opinion), but VERY willing, and pound for pound as tough as it gets in a fight with man. You can hurt him bad, and he won't quit.
The German Shepherd is the best of both worlds, as he has the size (80 lbs is just about right), he's smart, and also willing to go till it's over. He doesn't however handle the heat as well in some climates, and his drive doesn't quite match the Malinois, but there are exceptions.
Here's the difference however in these type dogs, and the pit bull, which is the topic here anyway.
The Shepherd, and the Malinois are bred to work "WITH" MAN", and the pit bull is bred for high prey drive, and tenacity, with just enough social breeding to be handled by man. By the way, a remark was made that a pit bull owner could wade into a fight between two pit bulls and not get bit! That ain't true friend. You will most likely get bit trying to seperate two male chichuachas doin it by hand.
The Poodle is considered to be at the top of the INTELLENGENCE CHAIN of dogs, with the German Shepherd in the top 5 if I remember correctly, and the Belgium Malinois being just below that.
The BULLDOG is at the bottom on intelligence, and is generally considered by trainers of working dogs, as the "class idiot", and the pit bull fits that bill. A pit bull's prey drive RUNS THE DOG.
But here is where the REAL DANGER is evident. A big German Shepherd when it's jaws are "about" closed, has a bite pressure of about 700 psi, to 800 psi. A Belguim Malinois is about 600 psi to 700 psi, while an average pit bull starts a around 1100 psi, and can go above 1300 psi.
Most SMART police dept.s have quit using Rottweilers for this same reason. LIABILITY! The Rotti is territorial, and has a "crushing bite". They don't handle the heat well, and the stress gets them quicker.
I'll give an example on stress. Take a well trained "drug dog" to search a car. Just a walk around search. Take a rectal thermometer, and check his temp. Then key him to search the car, and do the walk around search, then immediately take his temp again. It will most likely be 2 to 5 degrees higher. Why? Because dogs don't handle stress like people do. Their different than you think they are, and they don't think like us.
Now this is not to make you realize how smart I am, I ain't that smart. But I do know dogs, as it was my job to figure out how to get the most out of'em, and maybe pass a little info on to others.
Now with that said, I'm sure there's a trainer out there that may, or may not, agree with all, or nothing I said. That's ok. I know what worked for me, and very well.