In terms of passenger service, jwp is right, both directly and by type of example. It doesn't get much higher / thinner than Nepal! But they lose airframes regularly in A/c vs Rock tussles. Of course, that does create new demand for replacement elderly 1900-Ds.
. Same is true for hot & thin in Africa.
Size-wise, most management types believe in growth and planning for growth. The same is true for airline management, with SJS thrown in for good measure. True many places, but the smaller airframes fit well in places where the service population just won't support much growth (Paying the fuel bill to fly around empty seats just doesn't help the bottom line). Think: lower half of EAS, Alaska, even Nepal and African boonies.
I'll defer to my freight friends on the two Caravans vs one Beech. Speed over the ground is less a factor than cost per pound per mile (or per package, if that's the way the reimbursement bounces). Also look at the seasonal and weekly load variations, and service commitment - does it
have to be there tonight?