Best answer, IMO. It's better to think of the big bang emerging from a state where space and time have no scale. That seems to be what our models tell us anyway. When we say things like "our models break down before the big bang," that's because at t=0, our various measurements of distance and time become nonsensical (infinite, undefined, negative when they can't be negative, etc.). You hear that state described in a lot of ways--a cosmological event horizon, an exotic form of symmetry, a singularity, and so on--but it seems to me that all those describe a state where time and space just sort of fall away.

Edit: And I'd liken the question "how big was the universe before the big bang" to "how long did the pre-big bang universe exist before the big bang?" They are kind of both senseless questions to ask about the state of the universe at that point. They both presuppose that the universe at that point had such properties, but that doesn't appear to have been the case.