Lostpianoplayer, fantastic screen name by the way.
I know too little about 340's to get involved in the short field discussion.
Engine out scenarios at some point always end up in a very gray area.
A twin is only truly different from a single if you respect it's virtues and vices.
The second engine is only able to do you any good if you stay in a fairly abstract performance envelope.
I am currently in a job where we rotate at Vmc +5, climb at Vyse+5 and we do not allow operations from runways less then ASDR.
Having said that, here is the flip side of the coin. Probably some arguments that you are familiar with.
The engines don't know if you are flying over water. The engines don't know that you are flying at night. The engines don't know that you are attempting a very short field T/O.
Outside the above mentioned envelope you are essentially flying a single since the second engine will not do you any good. But then, most of us have several thousand hours flying in a single. We do not hesitate to fly at night, over water or take-off from a very short field.
So is it unwise to explore the envelope of a twin and operate outside of it?
Not necessarily. There are certain area's of the world where this is done on a daily basis. Alaska, Afrika, remote regions of SE Asia.
Here's a great example:
http://www.youtube.com/watch?v=Mhp0jbTpUGM
You just need to be very aware that if things go pear shaped, the chances of walking away diminish compared to a single.
No only weight and inertia is an issue, a medium sized twin can carry heaps of fuel and what I really dislike about light and medium twins is the awkward entry and exit for the pilot. No door on the pilot's side or you have to work your way through the cabin to get to a door. I have absolutely no statistics to back this up but gut-feeling would tell me that survival rates would go up if some more convenient exits were provided. some of the "bad" examples:
P68 Partenavia, look at the location of the door;
Rockwell Aero Commander, pretty much same door location:
One of the better ones, Twin Otter:
