Mark,
The real difference is what the Hebrew Bible says. Over and over it tells us how to atone for our sins (whether you believe it is full atonement or not). It NEVER gives us any other form of atonement. It never says the ways given would be for naught and in a couple of hundred years you'll have a new way. That is what are differences are. To us, the book is closed. If it's not in there, it has no meaning. It cannot be added to or subtracted from. You do have to admit, the xtian philosphy does "change" things in our bible a bit, doesn't it?