Bullmastiff or neapolitan mastiff?

The BM is easier to find, and although both breeds have hip dysplasia, the percentage or amount within the breed is VERY HIGH in Neos.  Neos have MANY more skin folds & therefore a LOT MORE SKIN PROBLEMS.  Due to (often DARKER coat) tend to suffer more cases of heatstroke.  The Neo is taller & heavier, much more stubborn, less wiling to please & is therefore harder to train, but also is more aloof.  The BM tends to need more exercise.

hello. Will you take good care of it and clear up all its poo and have its urine over you sometimes, dog train the dog, feed it best dog food, take it to the vet and spend much money when it is sick and speak gently to it? Will you get tired of it after 6 months? If yes, any will do.

You can't get homeowners insurance with ANY mastiff and/or an Akita in my State.  I'd check that first before you get a new dog (as opposed to an old dog).