Bonanza & commander
The Beech is probably the best built aircraft in its class but the running costs are large, if you are running a Beech as a business tool doing 200 hours + per year then I think that you could make a case for it because the quality construction would start to give a return in reliability.
The Rockwell commander is a bit sub beech, but the construction is not as good, the 112 is underpowered but the 114 has got things very well balanced and like the Beech is very nice to fly.
The big problem is keeping the six cylindr engine fed with £2/Ltr AVGAS.
You could not slide a cigarette paper between the R114 and TB20 in terms of performance and running costs, but in a very personal opinion I think the R114 is nicer to fly..........just!
It is a case of paying your money and taking your choice but in terms of cost I would prefer to give away a little in terms of speed and save some money by going for the top end of the Robin market, they may give a little away in terms of speed but the cost savings of an aircraft that will operate out of farm strips that the others will not look at gives the advantage of cheap hangarage and the chance of getting into a small strip near the intended destination, a fact that may well negate the higher speed of other aircraft.
There is a lot of misinformed prejudice against Robin aircraft, Flyingstone is a typical example of the people who have been fed a lot of half truth and misunderstanding and repeat it as truth, all I would say is go fly the Robin with someone who has done a few long trips in one and I think you might find it is the aircraft for your mission.
The last thing I would say is if you put two engines on a Bonanza it is called a Barron and this truly puts it in a class of its own.