Question: What was the benefit of reintroducing piston power and replacing the most popular turboprop engine in history?

Context:
Orenda OE600
The Orenda OE600 is a 600 hp-class liquid-cooled 8-cylinder V-block aircraft engine intended to re-introduce piston power to aircraft normally powered by the famous Pratt & Whitney Canada PT6 turboprop.
 The piston engine offers much better fuel economy, which Orenda Aerospace felt would be attractive for older aircraft whose engines were reaching the end of their lifespan.
 However, changes in Orenda's business in the post-9/11 time frame led to the project being canceled.
Vickers Viscount
The Vickers Viscount was a British medium-range turboprop airliner first flown in 1948 by Vickers-Armstrongs, the first such aircraft to enter service in the world.
 A product of the Brabazon Committee, it used a new form of propulsion, the turboprop engine, replacing the conventional piston engine.
Contra-rotating
Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque.
 Examples include some aircraft propellers, resulting in the maximum power of a single piston or turboprop engine to drive two propellers in opposite rotation.
 Contra-rotating propellers are also common in some marine transmission systems, in particular for large speed boats with planing hulls.
 Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission.
 The configuration can also be used in helicopter designs termed coaxial rotors, where similar issues and principles of torque apply.
Rolls-Royce Dart
The Rolls-Royce RB.53 Dart is a long-lived British turboprop engine designed, built and manufactured by Rolls-Royce Limited.
 First run in 1946, it powered the first Vickers Viscount maiden flight in 1948, and in the Viscount was the first turboprop engine to enter airline service, with British European Airways (BEA), in 1950.
 On 29 July 1948 a flight between Northolt and Paris–Le Bourget Airport with 14 paying passengers in a Dart-powered Viscount was the first scheduled airline flight by any turbine-powered aircraft.
Allison T38
The Allison T38 (company Model 501) was an early large turboprop engine developed by Allison Engine Company during the late 1940s.
 The T38 became the basis for the very successful family of Allison T56 turboprop engine.
Contra-rotating propellers
Aircraft equipped with contra-rotating propellers, also referred to as CRP, coaxial contra-rotating propellers, or high-speed propellers, apply the maximum power of usually a single piston or turboprop engine to drive two coaxial propellers in contra-rotation (rotation about the same axis in opposite directions).
 Two propellers are arranged one behind the other, and power is transferred from the engine via a planetary gear or spur gear transmission.
 Contra-rotating propellers should not be confused with counter-rotating propellers—airscrews on separate shafts turning in opposite directions.
Pratt &amp; Whitney Canada PT6
The Pratt & Whitney Canada PT6, produced by Pratt & Whitney Canada, is one of the most popular turboprop aircraft engines in history.
Rolls-Royce Clyde
The Rolls-Royce RB.39 Clyde was Rolls-Royce's first purpose-designed turboprop engine and the first turboprop engine to pass its civil and military type-tests.
Ryan XF2R Dark Shark
The Ryan XF2R Dark Shark was an experimental aircraft built for the United States Navy that combined turboprop and turbojet propulsion.
 It was based on Ryan Aeronautical's earlier FR Fireball, but replaced the Fireball's piston engine with a General Electric T31 turboprop engine driving a 4-bladed Hamilton Standard propeller.
Kuznetsov NK-12
The Kuznetsov NK-12 is a Soviet turboprop engine of the 1950s, designed by the Kuznetsov design bureau.
 It drives two large four-bladed (eight per engine) contra-rotating propellers, 5.6 m (18 ft 4.5 in) in diameter, and 6.2 m (20 ft 4.1 in) in the NK-12MA and NK-12MV.
 It is the most powerful turboprop engine ever built.

Answer: much better fuel economy