I am also enamored of the external hammer coach guns, but the more I think it through they do seem to present other problems. While you gain the advantage in storing the gun loaded but uncocked, you must cock both hammers to make the gun ready. Most guns (and the people who shoot them) cannot cock both hammers easily in one motion, meaning two separate actions. Most, if not all, have extractors, not ejectors, so even if you can flip the empties out quickly, you still have to load two chambers, close the action, cock two hammers and, in most cases, flip off the automatic safety.
With a hammerless coach gun, at least some of them, if you are concerned about the action being cocked, it is possible to drop the hammers on snap-caps, remove the forearm, replace the snap-caps with live shells, close it and replace the forearm, resulting in a loaded gun with an uncocked action. The gun must have
rebounding internal hammers to do this. Then you merely have to break the gun open, close it and snick off the safety to make it ready. Faster than cocking two hammers, IMO. Reloading merely means dumping the spent shells, replacing them, closing the action and snicking off the safety since the action has been recocked by opening.
One can always de-activate the automatic safety making it manual and eliminating one step in both cases.
All in all, I personally would rather have a single-shot with a hammer
and an
ejector than an external-hammered coach gun with extractors. Better yet, is a good basic pump, IMO.