Wow - I had no idea there were revised versions, but I would have been reading a few years after the revisions started, so I probably would have read a mix. I remember reading some old ones I had gotten from relatives, but also I remember saving up my allowance and buying some new ones, which probably would have been the revised ones. I guess I just wasn't a very discriminating reader in those days, because AFAIR, I liked them all...
Also not all that sure I'm a discriminating reader now either!
Anyway, someday now I'll have to see if my box of old Nancy Drews has survived in my dad's garage (!!!), and see which ones I really had...
ADD: The ones which really annoyed me were the Cherry Ames/nurse series. I never understood why she had to be the nurse, and not the doctor. So I gave up on those pretty fast.