I fail to see why it would be either or? In fact there are possible explanations based on String Theory that would explain the Big Bang.

I think you are mistaken because String Theory tries to explains the behavior of fundamental particles from the microverse to the macroverse (how they propagate.) Hence why it's called the theory of everything. It's OK if you misunderstood it because not even the experts on String Theory really understand.

What you just said isn't necessarily String Theory... Your proposed 11 dimensions is only a hypothesis within the main theory. String Theorists can't even agree how many dimensions there may be, with the most popular being 10 with another being 26 I believe. (In fact the proposed 10 Extra Dimensions states that the Big Bang was a symmetry-breaking event which was a fluctuation that caused the three spatial dimensions to break free from the other six dimensions, they then rapidly unfurled to produce our universe's observed 3D structure.) String Theory is a FRAMEWORK that unites quantum mechanics and general relativity (which we desperately need.) So what you just stated is only an offset of the framework that is the theory of everything.

String theory describes nature on extremely small size scales and high energies that are all but inaccessible to modern physics. The ideal experiment would provide direct evidence of these strings behaving in ways uniquely predicted by the theory, but that’s not as easy as it sounds, for two reasons. First, Heisenberg’s uncertainty principle puts some fundamental limits on how precise measurements can be. On the tiny scale of string theory, these limits may make it impossible to point at data and declare, “Right there, that’s a string!” as we can (or can approach) with the Higgs boson.