Since people like numbers, the general rule of thumb I've seen is that 80% of people shot with a handgun survive and 80% of people shot with a long gun do not survive.
Yes, it works both ways, HOWEVER, there's one thing to consider. From what I've seen, the experts suggest that most criminals are not particularly selective in their ammunition choices. So an informed defender using premium SD ammo may actually have an advantage (though probably not a large one) over an attacker/criminal.
From what I can tell, expanding ammo isn't really any more lethal--the biggest advantage, in my opinion, is that it's more "noticeable". What I mean by that is that non-expanding ammunition may penetrate through and through without causing any immediate pain or sensation, but that is less likely with good quality expanding ammunition. I think it's a significant advantage for the defender if the attacker realizes immediately that he's been shot. He might not be any more likely to expire as a result of being shot, but it could be a major factor in changing his priorities from trying to injure the defender to seeking medical help--and, as a matter of course, ceasing hostilities.