it is important to work out a mission profile and fit the aircraft to that profile whether its multi engine or single.
Other than how far? payload, range come a whole load of other considerations.
When will the aircraft fly! Day? Night? Summer? Winter ? over long stretches of water? Inhospitable terrain?
Some of us have to fly and turning up at 0500 mid winter in pitch black and taking off into a 200 foot cloud base and pelting rain? It certainly wakes you up with a jolt especially with the destination being the same.
Would I want a single? No thanks.
With the Seneca Fives we despatched and arrived at destinations with a success rate of around 95%. Fog was the usual deal breaker very rarely reliability.
I have flown in the TBM 850 an impressive machine which UK to Nice was only maybe 10 minutes behind the Citation cruising at FL280 and a solid 320 KTS but I would still be more selective concerning weather regardless of statistics which can be engineered to prove a point.
You also have to look at the PAX perspective! How comfortable are they with one engine in the same way as how comfortable are they with one pilot?
You can claim statistically to your PAX incapacitation is rare but does that reassure them? In my experience the same goes with the twin versus single argument some companies being reluctant to send their employees off in a single.
For me the Seneca FIVE is a mini Kingair and a trusted servant which I have flown in every kind of weather imaginable but you need to look at the mission profile first and what the aircraft is supposed to do before making a decision
Apart from Piper and Barons and the Diesel Diamond Twin Star there are few twins which are current and you have to go back to the 80s for other choices.
Pace