" I've read the LeF is not so strong, but seems to be virtually the same, just different lever operation. Or am I misguided?"
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You are misguided to some degree, because the Lef and the Jones underlever are NOT virtually the same.

The main profound difference between these two bolting systems is that the Lef. employes only a single bite or grip on lump, for weaker bolting, while the Jones employs a double screw grip bite, for considerable strength in bolting. The Jones pulls the lump/barrels down strongly, while allowing no, or very little, metal needing to be removed from the action, beneath the standing breech, the weakest area of any action, an area subjected to the greatest stress upon firing. Therefor, the Jones provides very strong bolting, while allowing for a very strong action, solid steel area beneath standing breech.

3 bite snap actions require a slight bit more metal to be removed from the aforementioned area on action, but that is in an area not subjected to much stress, high up on the rib extension area on standing breech, yet leaving enough metal to allow for a very strong action, with one additional bolt in an area most suitable for that bolt, the rib extension. That gives even more strength to the bolting of that Jones system.

Seems to me that you are discussing two different concepts, mixing them together, action strength verses bolting strength. Too, if considering action strength, the quality/strength of the steels used is paramount. The above concepts apply only if same metal is used in all actions.