I have both and prefer the X-570. They are almost the same camera, but the X-570 is just a little simpler and the available full-auto mode of the X-700 doesn't do anything for me. I don't know if it is just my camera but, in manual mode, the X-700 finder continues to show only the meter-recommended shutter speed, while the X-570 shows both the recommended and manually-set speeds. I find that very helpful.
That being said, a week after you get either one of them you won't remember any difference, so just get the one in better condition. And if you can find one, get a Motor Drive 1. It completely transforms the ergonomics of these cameras.