koghiensis show many much more leaves. And pretty erected leaves ! brown/orange colored new leaves for koghiensis. Much more bigger fruit for grandiflora. Much more space between grandiflora's leaflets. Don't need to talk about the size of the grandiflora's inflorescence... Grandiflora is pretty rare in the wild and in cultivation.
According to this pic I'm pretty Sure this palm from Jeff is a grandiflora. Couldn't be dumasii due to inflo/infruct. Couldn't be koghiensis due to crown area and size of existing fruits.
There is something I would like to clarify. I said grandiflora's inflorescence are bigger than koghiensis. That's right but not so much. Most important difference is about flowers themselves. Really bigger on grandiflora. An other thing is that koghiensis inflo/infruct have many much more "stem" than grandiflora.
Those differences (number of "stem" and size of flowers) could be easly seen on those following koghiensis pics. For grandiflora's flower size reference please take the new cal palm book and take a look p67 plate27 picD with Jean-Paul Tivollier.