Why is the 60-year-old NK-12 more fuel efficient than Europrop TP400?
The source of the Specific Fuel Consumption in Wikipedia is unclear. I have found a paper (PDF) that discusses the efficiency of shaft power off-take (that is using engine power to drive systems such a electric and hydraulic generators instead of delivering propulsion). 

It mentions the TP400-D6 (which is installed on the Airbus A400M) has a SFC of 0.167 kg/(kW.h) for shaft power off-take and a SFC of 0.213 kg/(kW.h) for delivering propulsive power. This means that the TP400 is more efficient than the Wikipedia article presents and more efficient than the SFC of the NK-12 presented by Wikipedia. 

It also shows that the TP400-D6 is more efficient in delivering shaft power than in delivering propulsive power.