Originally posted by Rondec The assumption is that you are using one format to recreate the shots you take on another format.
Yep, and I don't agree with this assumption. I think it is wrong of a photographer to say "I want to recreate the DoF I would get with a different format!" ignoring composition, exposure, motion blur, etc. This is why I don't agree with the DoF equivalence being the base for comparisons. Why base your photography on the wish that you want to make photos that look as if they were taken with another camera? This can only lead to unhappiness
And as you said, the other thing is that usually photographers need a thick DoF. Very rarely is a photograph bad because the DoF is "too big", but often a photograph gets ruined because the DoF is too shallow. Only times you need a shallow DoF is for one type of subject isolation, but even this is limited. A 50mm or 85mm f1.4 lens on APSC is more than shallow enough. But for most other genres (macro, sports, landscape, still life, wildlife) you want a wider DoF.
Regarding some of the earlier comments, I agree that FF has its uses, especially when it comes to improved noise performance (due to larger possible photosites) and wider possible angles (this advantage is shrinking, though). But I see DoF as fairly low on that list.