Arguably the strongest action by far for a double - the Bradshaw.
The underlever & the under dog in this discussion & I must say I really like it a lot.
https://bradshawgunandrifle.com/rising-block-double-rifle

It would be interesting to see speed wise which would be fastest, but I would suspect that would basically come down to familiarity.
My Merkel is no where near this class & still quite stiff.