Maybe both? A 2 part epoxy for the broken joint, clear to reduce visible repair. Then once that's cured, lay it face down and layer some JB Weld on the back side, kinda like a bandaid. There's a nice recess on the back side where you could actual smear a couple of thin layers to give the crack repair some stabilizing/rigidity.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)