i own a bullmastiff and they are fantastic dogs. loving and kind. they can be a bit aloof with strangers. i would have another in a heart beat. they need to be socialised when pups and need training as they can be stubborn at times lol. they are clowns though.

i have also fostered english mastiffs these are bigger than the bullmastiffs. they again are aloof with strangers. need training and socialising from a young age.
if i had a choice english or bull i would choose the bullmastiff imo.