B1900D uses PT6A-67D, rated 1200SHP.
350 uses PT6A-60A, rated 1050SHP.
1900D is a bit heavier, but it's negligible (10%, is less than power difference). Initial climb rate is pretty much similar as well. It's the cruise altitude that makes difference - assuming both cruise at approx 190KIAS, 1900D at typical cruise 16000-17000 would be like +33%, 253KTAS, while 350 going all the way to say F320 would be at +64% with a whooping 312 KTAS. So, the difference is up to wing, induced drag, pressurize system and altitude.
There is an old saying; if it looks right, it probably flies right.
Hence.... King Air 350 ….versus 1900C …..versus 1900D
The first is a greyhound, the second a saluki, and the third is a beluga whale.
What is somewhat surprising are the contrasting specifications.
The King Air 350 weighs in at 10,000 lb OEW with 11 seats, which is a whopping 1100lb more than the 10 seat King Air 250. That is a lot of extra weight for one extra seat and a pair of windows. (ok, there must be other differences too, but it appears luxury and space was given a priority over weight)
Hence comparing the weights of the 350 against the stripped out 1900D comes from a poor starting position.
Both the 1900C and D models are considerably longer, but for me it is the 1900D's higher roofline that is the defining feature, and precisely the reason why it is so abominably ugly.
For me, the Beech 99 was a closer approximation, squeezing 15 pax into an airframe with dimensions similar to the 250/350, but stripped out so that it weighed less than a bag of marshmallows. On top of that, it only had engines with less than half the power of today's 1900s.
This engine/fuel efficiency came at a cost though; cruise speed was way down.
I haven't found specific data for the 1900C except for the engines which are rated at 1100 eshp (as opposed to 1279 eshp for the 1900D).
I humbly suggest that most of the extra 179 shp is purely to overcome the drag from the higher roof.
But at the end of the day, as a passenger, if I can't have a 350 all to myself, give me the 1900D.