Ah, that's a question. And probably the key for the opening of a can of worms! After all, talking about editions can easily lead to passionate debates about historical accuracy and scholarship... Never mind any discussion about whether BWV565 is by Bach at all.
Anyway, I would suggest that the ideal perfoming edition (of any music) should have these qualities:
- based on recent scholarship (last 30 years - preferably an edition labeled 'urtext')...
- ...BUT editorial marks should be unobtrusive
- laid out in a legible fashion (including page turns).
- printed on high-quality paper (you will want to use this music for decades)
- bound so that it will lie flat on the music stand without requiring excessive violence to the spine (of the book)
For Bach, I have a couple of volumes of Baerenreiter, which are excellent in all these respects - along with an inherited collection (almost complete) of Novello. The Novello are useful for reference, but are encumbered with 19th C phrasing and registrations - and lack BWV numbers. If I am learning a piece for performance, I would prefer the Baerenreiter.
That said, it is of course possible to prepare a convincing musical performance from any edition - though it is easier to use a good one. In part, it depends on your budget - the cheapest thing is to download out-of-copyright editions from IMSLP for free.
Have fun choosing!
Ian