Generally, the question is NSX vs Contrail, not NSX versus EVPN. I think you are really asking OSVDB vs EVPN. EVPN is an open standard, which should [eventually] provide interoperability between different vendors. OSVDB came from VMWare, via Nicira, and I think now is IETF draft standard. Many switch/router vendors, Juniper being one, support OSVDB (and EVPN as well) to interoperate with VMWare, but this may only be on a limited set of products.
As far as I know, and what little I know, NSX and VMWare are both generally closed systems. So if you expect NSX to manage other types of VMs (KVM and HyperV come to mind), that is unlikely to happen. This is a major difference today between NSX camp and Contrail.
Containers may change all of this, . . .