Internal WAN core network addressing, public or private?

Hi, all, we are planning to build our own WAN core network, the links between data centers will be point to point (dark fibers + virtual circuits), how do you address those P2P links? here is the pros and cons I can think of if use public space:

Public -- pros: traceroute can always work, don't need to worry about overlapping with internal networks down the road, cons: need to burn extra precious public IPv4 space we own, also need extra security care at edge of the network as now the core network might need to be visible to wild Internet.