Unless one clamps the action to a vise and measures the force on the barrel to shear off the bites, we can only speculate.

Suffice to say, both are very strong but are compromise in that the notched lump has square edges and that creates stress risers that can case the lump to break off, and at the same time allowing fast opening.

Merkle, by the way uses a radius on its inner lump.

The greener cross-bolt transfers the load to the best mechanical advantage greatly reducing the stress on the lumps.

If it makes you feel better, virtually all side by sides still use the Purdey double under bite.