It's okay, I get what you're saying - that's a pretty big price differential. You're sure that brightness and contrast are the same? So the only discernable difference between the two screens is the auto dim and the hdmi and 5 wire touch?
If so, that seems like an awfully big price difference. I'd be pretty tempted to buy the Mini 700. But with that said, I can say that I've only owned two screens ever - an Earth LCD that lasted 6 months (my fault) and a Xenarc 8" that has lasted since about 2006. Still works and spent several years in the car.
I recently rebuilt my setup and put the Xenarc back in the original case. You can't tell it was ever out and it still works great. YMMV, but if the Mini 700 turns out to be a piece of junk, you'll have to decide whether to buy a replacement, and the price differential becomes a premium for an experiment in low cost electronics.
Tough call. I think I still might go with the Mini 700 and take a close look at it when you pull it out of the box, then return it if it looks pretty cheesy.