If you had to choose, would you rather spend money on overdyed floss or hand-dyed fabric?
Actually I think my vote goes to the overdyed floss, I don't use so much hand-dyed fabric - partly because of availability and partly because I often seem to get the piece that looks very odd when I do order it specially.
But thread is another matter indeed - I have good collections of GAST and WDW, plus quite a bot of Thread Gatherer, Crescent Colours, Caron Collection, Olde Willow Stitchery, Needle Necessities and Dinky Dyes. The only overdyed ones I really don't like are the DMC ones, I think they should stick to what they do best. At the moment I am in love with Belle Soie from Crescent Colours and am seriously thinking of expanding to a complete collection of that. I tend to buy for specific projects and then fill in gaps as and when the mood takes me.