Hi,
if you have only private connectivity on some sites (towards core segment - zone) and it is single connection, SD-WAN only has advantage to have one centralized management and monitoring system. You will not have routing advantage and you may use traditional routing without an issue.
In general, all these depend on business/technical requirements. Do we need good centralized management and monitoring system? Do we need security (IPSec) between sites (from InfoSec point of view it can be mandatory)?
HTH,
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