[Cozumeleno]

To me, it depends on how rare of a back you're talking and how low-grade.

If it's a fairly common version of the rarer backs (Sovereign, Old Mill black, Polar Bear), I'd rather have the Piedmont/SC. That would probably apply, too, even for rarer backs with severe paper loss, excessive ink marks, etc., unless it was something really rare like Broad Leaf, Hindu, Drum, Uzit, Lenox. Something like a Tolstoi or EPDG missing like half of the back doesn't do much for me.

I guess for the purposes of the question, I'd say the rarer back as long as we're not talking something pretty common or a card pretty destroyed.