Each design has it's pros and cons. The conventional 103 I am working on only has around 1/2 of it's surface area in the wings. That's a lot of parasitic drag that could be lost. But a BWB would not achieve as high a CL as easily, so I wouldn't see a 50% drop in parasitic drag. Conventional planes are better suited to E spanloads, so they have less span for a given induced drag. But they'll be heavier. There are no best choices. At the end of the day, there is the sum of the parts. That is why there has been such a variety of aircraft shapes.