The Jones underlever has imo the best lockup for longevity, but it is clumsy to use, hence the need for the evolution to the top lever.

I have never been a fan of a trigger guard snap lever, or the Jones on a double rifle. I do however like very much a side lever snap action design [on a shotgun

], in this design you just thumb break the action open [sexy]. BUT were talking double rifles here, which are designed to fire quickly, as such there is no substitute for a top lever.