U.S Car Tool sub frame connectors install
Another factory I worked at built seat frames for the automakers. They would run tests with machinery designed to repeatedly stress welded assemblies. The equipment would run day and night, simulating the amount of wear and tear that would accumulate over years of use.
They looked for optimum weld placement for the most longevity and where to design in flexibility (if needed to negate too much stress in other areas).
I know that every part made isn't engineered to perfection. But most companies that make parts for the automotive industry will spend a ton of money trying to design against breakage because of the cost of liability claims.
I'm not a structural engineer but from the designs that I've been familiar with I would tend to believe that a stitched weld would work best on these connectors.