I won't pretend to know about all L410 derivatives, but the company I work for has 2 L410 UVP E20s. The fuel flow is approx 150 KG per hour in the cruise, not litres per hour, and all four engines have returned this consistently over 6 months of use, looking at our engine monitoring logs. The are very reliable, although require some small time to idle before shutdown, which is believed to have been the cause of one combustion chamber failure recently diagnosed during routine maintenance. I have no experience of the PT6 to compare, but many have commented that our engines are quite noisy, especially on start up.