I mean, is this even a question. I didn't think it was. Sausage rolls are the absolute bomb. The pinnacle of Australia. Tomato sauce. BBQ sauce. BOTH. Sausage roll. Done. Perfect day achieved.
But no, some people prefer those little pockets of minced disappointment. So the question must be: party pies or sausage rolls?
As much as I am shitting on party pies, I do have some supremely fond memories of the full-sized versions. It used to be a treat after 9 holes on the Picton golf course; I'd wander up and down the fairway (sometimes with a reasonable measure of success) with my dad and godfather, and the latter would sit and teach me the proper manner on eating a meat pie afterwards with a schooner of pub squash. (Solo, basically.)
But for the mini variants, sausage rolls all the way. They're easier to eat, a bit more consistent across the board, and just all-around reliable. Anything that is a receptacle for sauce entering your mouth never fails, especially if pastry is involved.
What's your preference?