The Zyxel's are based on Qualcomm Atheros chips capable of a maximum PHY rate of 1000 mbps. The D-Link is based on a Broadcom chip, that has not yet appeared in any widely available shipping product, capable of a maximum PHY rate by utilizing a wider frequency band.
At this point, there's no reviews I've seen on any products based on the newer Broadcom chip so there's no guarantees that it will actually be any faster in real world scenarios.
Interesting, thanks for the reply! I'll just have to wait and see how it performs upon release.