I’m quite late with the current Stitching Blogger’s Question, which is:
Overdyed floss, certainly. I’ve only purchased one piece of hand-dyed fabric, and nobody is likely to go, “Oh, wow!” about the effect in the finished piece (although I’m happy, because I couldn’t find any other fabric that was exactly right). I seriously doubt that anyone but another devoted stitcher would ever know that the fabric is hand-dyed.
The overdyed flosses I’ve used, though, frequently lead to incredible effects that are apparent to anyone who views the pieces. They’re usually a joy to work with, as well.