Hi Hawks,
The top stone is definitely the best as far as light return is concerned, but it's still quite green (light reflected from low angle side light).
I think I would want a princess with at least 75-80% red in the ASET
BUT!!!!
Keep in mind that the ASET isn't the whole story. You want to make sure that the idealscope (IS) image (the red one) is all red and few or no sections of grey. Here's a stone with a pretty aset but a minor amount of light leakage (grey facets on the IS image) http://www.whiteflash.com/loose-diamonds/princess-cut-loose-diamond-3036240.htm