Well if you know the differences between each are, I don't fully understand your question. Both the DDock and DPort work with the Monitor stand. Just ask yourself these questions:
Do I need an extra modular bay?
Do I need the PCI slot?
Do I want an integrated power supply with the DDock or do I want to have an extra power brick that comes with the Dport?
Mind you on the monitor stand. The DDock sits underneath the monitor and the Laptop.....not so much. My D820 is about 1/3 under the monitor stand and 2/3 of it sticks out in front (good thing my desk is almost 40" deep) The DPort is small enough your laptop will be completely underneath the monitor stand.