What made the 2707 so superior?
The plane was designed for a US funded competition which it won, after it would get 1 million dollars in funding for further development which automatically means that the 2707 would be the cheaper plane to buy and that it had the US Government Stamp of Approval. This also meant that there were political reasons to commit to buy one of them.

The reason it won that competition is because it was slightly less loud, slightly more efficient and more technologically advanced than its competition.