Bullmastiff would be my choice out of those dogs. I think corsos and ddbs are more poorly bred than the others. In fact I'd say those two breeds are being more poorly bred than just about any other breed at the moment. I'm sure there are exceptions, but holy crap do they seem hard to find. There's nothing inherently wrong with the breeds, they've just drawn the short straw as far as the calibre of breeders that were attracted to them. They're just awful snake oil salesmen as a general rule, cashing in on exotic unusual breeds. Boerboels are another one. EMs and bullmastiffs being more boring don't attract these shifty dishonest money making breeders. Which isn't to say they are being bred well compared to serious working dogs, but as far as purebreeds go the more boring ones typically aren't bred as badly as the more exotic and unusual ones. Bullmastiffs is the safest bet there IMO, although still far from a safe bet, there's really no such thing in the dog world.