The MSI MAG B860 TOMAHAWK WIFI wins in 5 out of 14 comparable specs, with 5 ties. Its biggest advantage is USB Type-C (100% better).
MAG Z790 TOMAHAWK WIFI wins in 4 specs (SATA Ports: 75% better).
Recommendation
Choose MAG B860 TOMAHAWK WIFI if you want the best overall performance — especially usb type-c.
Choose MAG Z790 TOMAHAWK WIFI if sata ports matters more to you.
