Look for three things: factory-applied shrink wrap with even, tight seals
To me, another big knock on Unhinged is that the set is really, really underpowered
Keep in mind: more than anything, I'm looking at Pokemon cards for investment purposes, not as collectibles or as a card game (although I do look at them from those perspectives as well)
Niv-Mizzet, Supreme ( F ) - A lot of the words on this version of Niv-Mizzet are not very useful for Ur-Dragon
A gigantic Rayquaza flying through the sky, and featuring a reference to the rather obscure OmegaRuby and AlphaSapphire character Zinnia, Rayquaza VMAX highlighted the dragon theme of the expansion particularly well
For border extensions, you can make a little O of tape and stick one side to the work surface and the other to the back of the card