The lower essence cost is the main benefit of delta-ware. Any other benefits would be up to your GM.
So really it is going to be down to a deltaware metahuman or a crapware cyberzombie with really high attributes?
As soon as you cross the Zero essence barrier you're either dead or have to become a Cyberzombie. As I detailed earlier, you can have a Deltaware Cyberzombie, but it will be difficult to fill out the essence cost to -12 without getting lesser grades in some regards. Also, if you remove Biocompatiability, the Essence cost rounds to -11, which is pretty low.
One last thing, the cyberzombie doesn't get a bonus to attributes equal to how far below zero he is. He gets a bonus to his natural attribute
maximums equal to how far below zero. He still has to raise those attributes through other means.