They're somewhat complimentary. I've got both running along side each other. Wireguard has much better throughput, but tinc guarantees a fully connected network (each node can reach every other node).
I wish wireguard could accept overlapping AllowedIPs ranges, appear as an L2 interface, and take a nexthop from the system routing table. Imagine multiple hosts each providing egress to each other - tinc can do this topology when setup to act as an ethernet segment. But wireguard is so trivial to setup, it's easy enough to run a parallel instance for each horizon.
One Tinc advantage is that it can run on an Openwrt router.