Interpreting Bach can be a very controversial subject.
Here's a brief history, (that I will say is ~90% correct! ;))
When Busoni created his edition, performers in general had much more liberty on how they played pieces. The generation of performers after Busoni started putting more emphasis on playing exactly what the composer had written or intended, and on historically accurate performance styles. Now when Bach wrote the WTC, he did not have a piano - he had organ, harpsichord, and clavichord. The clavichord had the ability to play graduated dynamics, but the harpsichord couldn't - some of them had an extra set of strings that could be added to make the sound louder. When I first learned how to play baroque music I was taught that I had to use terraced dynamics, meaning a section would be played piano, and another section would be played forte. I was also taught to play the notes detached, as if I was imitating a harpsichord, and no pedal was allowed. My general instruction now is to make the piece sound good using the instrument I have - the piano. And because it is a controversial subject, I'm still confused on how to play Bach!!
So going back to Busoni - what you have in his edition is Busoni's interpretation. If you played it as specified in his edition, it might come out sounding too much like a Romanticized piece of Baroque music. That said, I like looking at these editions because they can give ideas on how to make the piece more interesting. It's kind of like having a lesson with Busoni.
