Folks,
As the old story goes: What is the difference between a DC-6 and a DC-7??
One is a four engine aeroplane with three blade props, the other a three engine aeroplane with four blade props.
The story of the R-2800 is very interesting, in the development/early production days, there were severe harmonic vibration problems, but some very smart people got to the bottom of the problems --- and the engine in service developed the good reputation mentioned here. For anybody of an engineering bent, the development story, and harmonics never observed before, and their cure, is a fascinating story.
In one day in the QF history, every Connie was on the ground somewhere with an engine failure. Mum and Dad spent almost a week, living in the "old" terminal ( a single story brick building) in Bahrain, waiting while an engine was sourced and changed on a 1049G. Qantas variously used a Lanc. and Liberator as full time engine carriers.
The reason you don't hear much about "transport" Merlins was their very low overhaul lives, and general unreliability. 500 TBO targets were rarely achieved --- when Wright R1820 and P&W R1830 regularly made 2600h. In the Qantas Lancastrians (which had to be use on "colonial routes", because US built aircraft were not permitted, in those days) an engine surviving two round trips to London from Sydney was usually about "it".
The Argonaut, a DC-4 re-engined with Merlins, was a dog of an aeroplane.
As for the pom sleeve valve engines ---- the answer to why there are none in service, but still plenty of P&W and quite a few Wright ought to be obvious. Darwinian selection!
Tootle pip!!
PS: Feather 3,
A big increase in the PRT turbine clearances doesn't hurt, and having hydraulic props. is definitely a "good thing" compared to electric props.