Piston transports needed a fair bit more 'management' then their jet counterparts, especially fuel systems.
The DC-6B for example had either eight or ten fuel tanks, requiring dedicated attentiopn by the Flight Engineer for optimal operation.
This, together with shifting blowers, modulating oil shutters and cowl flaps (not to mention the ignition analyzer) kept him fairly busy.
In the end, this one Douglas piston transport was certainly the most reliable, and had the lowest operating cost of any.
The DC-4 wasn't bad, either, although just a tad underpowered.
DC-7?
OK, except for the engines, which seemingly had a mind of their own...failing PRT's with uncommon regularity.
1649 Constellation?
Very complicated, but a good performer...typical Lockheed.