Both String Theory and Brane Theory have been shown to yield equivalent results to the Standard Model (QFT). Nowadays physicists choose the model yielding the simplest computation for the problem at hand. No contradictions have been found after years of doing this.
So you're saying they're the same theory disguised as different, or another facet of the same solid, only useful as a computational shortcut. Maybe it's time to look for contradictions?
I'm not a physicist, just a knowledgable enthusiast. To your point, people are trying to look for contradictions. So far, none have been found. Physicists therefore use the model that simplifies the computation. If a contradiction is ever found then that will provide information as to which model is correct.
