I read meters in the ghetto suburbs of Chicago, you are right about most of the dogs being all show. One of my worst was with a chow, one with a dalmation also, and the last one that sticks out in my head was some mutant Pit. Beleive it or not all the bites were from the few days I actually read in nice neighborhoods. I tend to find that the worst of the dogs were usually owned by assholes and treated them like shit. German Shepeards were one of the few dogs that would ever scare me, smarter than they should be. Badly treated dogs tend to turn on their owners quite often, I guess that's just Darwin rearing his ugly head.
Good luck on finding a mean dog, I just hope you don't fall into the ASSHOLE class.
By the way, I have a 200ld Mastiff that could tear my arm off laying next to me licking a stuffed Santa, don't base you decision on the breed, this thing is a pussy.