QuasiUnaFantasia
For a couple of decades I only knew Glould's rendition of the WTC, and I thought his way was the "correct" one. I also found his rendition about as exciting as listening to a tumble dryer (and not necessarily one in operation either). Then I ventured out to get Barenboim's version (I always loved his Beethoven), and - lo and behold - I thought it sounded good and interesting! Later I also heard Nikolayeva's version of the "Little preludes", and I thought she played them brilliantly; they sounded pleasant and engaging.
With respect to what Bach himself would have wanted; he used the most moderne instruments available to him, didn't he? So, had they existed, he would probably have used moderne instruments as a matter of course, and with pleasure taking use of their possibilities.