I haven't prepared lobster since my last chef's job, primarily because I don't like eating it anymore. Like veal (and to a lesser degree lamb) I've lost my taste for it, and haven't eaten it in years.
But as soon as I was able to make decisions about how to cook things on the job on my own I always chose to kill lobsters by killing them with a knife before cooking them or dismembering and shelling them for raw meat preparations (e.g. ravioli or sausage). I never bought that line about how they don't feel pain and blah-blah-blah: maybe it is true, more likely it isn't. I reason that whenever one is unsure of how to kill something the best thing to do is to choose the method that is most likely to render the least pain: dropped live into a pot of boiling water or rendered insensate and dropped into a pot of boiling water?
The method of killing lobster depicted here is the method I used prior to shelling the lobster for raw meat preparations. For boiled lobster, I inserted a knife between the head and the thorax to minimize the loss of "flavor" to the cooking water.