anastasia:  Our neighbors had big aggressive dogs.  I think they were just being territorial and since we had dogs to maybe we were "the other clan."  But I was determined to be accepted by them so I bought some big size doggie treats and offered my peace offerings at every opportunity.  Now their dogs come to visit me.  I have the treats by the door. 

I think small dogs have a tendency to be more high strung and agressive (certain breeds).  I know our smallest Yorkie was like this.  She was a mini but would go after all the big dogs (thanks for the fence which helped her be brave).  She didn't even have any teeth to bit with but she'd bark bark bark at anything that moved.  My experience with larger dogs has been that many of them are far more easy going than the little ones. 

That said, I personally don't feel comfortable with larger dogs unless I know them.  And even my own midsize dog I kept at bay when it came to my grandchildren.  It wasn't worth the risk.  I don't think she (part Spitz part Blue Healer) would have hurt the kids ever, but I was always careful about it.  She was agressive towards strangers and she and I had a battle (which I eventually won) over who the Alpha was to be.  She never bit anyone (nipped at me once when I stepped on her tail...can't blame her). 

I have no more pets now.  The dogs have died and recently the cats have disappeared.  We have no idea what happened to them.  They were always at the door for their meals and at night would come into their little beds (they were the neighbors cats .... long story)  ;)  I'd love to get another one but wifey says no and since the neighbor has plenty, I do get my daily dose of animal contact.  (they even have goats lol) ;)