When talking about history there are very few "correct" and "right" answers, since one would have to first define what one means by "Germany" and "Austria".
I believe the Hapsburg monarchy controlled a larger portion of it than the Prussians, so it technically it's closer to Germany having been part of Austria than the other way around.
Of course it is even more accurate to say neither is true, since the holy roman empire was more of a loose confederation than a country, i.e. closer to something like the EU than to Germany or Austria.
And what about East Fracia, or even the Carolingian Empire itself? Austria & Germany together.
That's the thing with this history stuff, it's rarely as clear cut, nor are today's examples (e.g. modern Germany, EU) totally relevant for examples of the past.
When talking about history there are very few "correct" and "right" answers, since one would have to first define what one means by "Germany" and "Austria".