We used to attach vmks to VLAN segments on the NVDS. Since NSX on vDS, we ask users to attach them on "standard DVPGs", meaning, the regular DVPG of the VDS. We're in fact hoping to deprecate the NSX VLAN segments in the future. I'm not sure what this means for support (because support team tend to be strict on those kinds of things), but I can tell you that there should be no difference between standard DVPG and NSX VLAN DVPG for your vmk attachement.
There is one area where this is important though. In the above diagram, you have an edge VM running on a host prepared for NSX. You need to attach this VM to NSX VLAN trunk DVPGs, a standard trunk DVPG would not work (at least for now.) This is very specific to the edge VM. Again, there should be no difference for your vMotion vmk.
Are you sure the NSX VLAN segment and the standard DVPG you tested vMotion with were using the same physical uplinks? They have different teaming policies.
regards,
Francois