OSPF etherchannel between core routers

[hellomo]

I have two core routers at Site 1 and two core routers at Site 2. They are in OSPF area 0. They are considered my campus cores with multiple distribution routers connected to them, each with their own area. For the cores at each site should I build a link between them (2x40G) as an L3 ether-channel or as separate links. Diagram below. The green represents OSPF full neighbors. Which Site is considered best practice.

[paul driver]

Hello
Personally id go for ECMP rather than a LAG, it will have a faster failover time and much easier to control the traffic if the need arises to policy route or path select on certain traffic/link