The Bull Mastiff is one I love and miss having. I will, again one day, own another pair.
This is what AKC says about them...
Working life
With its handsome and powerful appearance, along with surprising speed, coupled with incredible strength and endurance, Bullmastiffs can overtake and capture intruders without mauling them. These traits make the Bullmastiff appear to be an excellent choice for a guard dog; however, a stubborn streak makes the animal somewhat resistant to obedience training and they can be overly protective of their human family. Due to this, the breed has been overtaken by others, more popular as guard dogs. Bred to sneak up on poachers, the Bullmastiff barks much less often than other breeds, but when they bark they will make your head turn, as it is dark and hollow sounding. The Bullmastiff was recognized as a pure-bred dog in 1924 by the English Kennel Club. In October, 1933, The American Kennel Club recognized the Bullmastiff. The foundation breeding was 60% Mastiff and 40% Bulldog (which was the Old English Bulldog, not the modern short English Bulldog of today).
Mine were not difficult to train, but they are, like mentioned very protective of their human family. My male, Sam, would get between me and the door (nicely, but ready) when someone would come up. And always had to sit on my feet. They were never aggressive, and Onery loved the shows. One thing though, they never really learned they were big when they grew up. I learned from the experience of my 1st that you can't allow them to do anything while they are little that you don't want them to do when they are grown, or you may find you have a 150 pound lap dog! LOL!
Plus they come in many colors, which I enjoy.
Color
Any shade of brindle, fawn, or red is allowed as long as the color is pure and clear. In the United States, however, there is no mention in the standard of the color being "pure and clear". The fawn is a light tan or blond color, while the red is a richer, red-brown. This can range from a deep red to a light red merging with the fawn sometimes described as a red-fawn. A slight white marking on the chest is permissible, but other white markings are undesirable. A black muzzle is essential, toning off towards the eyes, with dark markings around eyes contributing to the expression
I've had many breeds in my life, I always find myself interested in the working class group, I love all of those.
On the other end, the Tiny Teacup Pom. was a breed I enjoyed having. But none could match Kibbles in that breed. :~)
My all time favorite was my Pit Bull/ Border Collie, Jynger. But she was just special, I don't think it had much to do with the breed.
Wish I had pictures to share, but they are packed.
I am sure, that with this research you are doing, you will find the breed that best suits your needs and desires!
~Karen