Hi Bill,     You wont lose any feature , as you have said the vmware API is integrated in vnxe. So it automatically formats and is visible on your ESXi host when you use the vmware tab. But in generic ISCSI you have to manually format it. Otherwise replication works for both using Replication manager.
In the VNXe Unisphere GUI, under "Storage", we can create a (generic) "LUN" or a "VMware Datastore."  I realize that the latter option will create the LUN, format the VMFS-5 file system, and present to the ESXi hosts, which is great.  But other than these extra "convenience" features, is there any material difference between creating a (generic) LUN and assigning it manually to ESXi hosts (and formatting it as VMFS-5 inside ESXi), versus creating the "VMware Datastore" in Unisphere?  In other words, do I lose any important technical capabilities, such as VAAI, if I create a generic LUN vs. a specific "VMware Datastore"?
Difference between creating "VMware Datastore" and generic LUN in VNXe 3.x?