From my readings into boards lately the only major difference other than the keys is that the DZ60 has underglow RGB (I think it's 8 LEDs under the board). The GK64 has underkey (on top under each key). Other than that I think every thing you said is everything I have seen on google.
Personally I'm going with a DZ60, Gateron Blues, and currently looking for a nice case that will work well with my underglow. Otherwise I have to build a case. I was thinking about using my 3d printer...
Sorry for a late response, I just joined and was scrolling through and found your post.