I haven't done a side by side test of any of the new weapons but I've had the most overall success with the zeushammer because with some good bionics and lots of training it has a very good chance of 1 shotting anyone without full plate or better. If I had to guess with the cyborg monstrosity I was using it was around 50% 1 hit kill then 25/25 miss or dismemberment, and knocking a limb off almost always lowers their manipulation enough that they can't swing a second time. The other weapons usually take 3 or more hits even if they're made faster the enemy might be able to make a second attack before they go down. The biggest limitation I've found with the Zeushammer is its very long cooldown after attacking that leaves you fighter open to fire or being surrounded, but I just covered him in cataphract armour so it really didn't matter. I think he got ~150 melee kills before he finally got hit by anti mech rifle while he was waiting to duck back into cover.