8mm fisheye vs 7mm fisheye? - 1

1) vivitar 7mm fisheye = $315
2) Rokinon 8mm fisheye = $280

A have a cropped sensor DSLR (Nikon D200) So I want to get a wide as possible.

My question is, is the 1mm really that much of a difference? And If you had to choose, which one would you get?

I'd chose the best build lens. Cheap fisheyes tend to be very challenged in that matter.