Interesting question: I remember having read long time ago, that Russian-built airliners tended being underpowered respect to their western counterparts, this resulting in slow climbing and other operational difficulties for air-traffic controllers.
Also, the USSR airplanes' instruments were metric; besides pilots say that feet are a bit more accurate in estimating height for things as precission landings, one meter is around three feet, also a mile is a minute of arch, no match between a km and arches, some problems resulted, for example, in places where metric units were used for fuel. For those having a local way for measurement, it's easier adapting to using it plus another more universal system than the reverse, from the general to the private, habitudes are hard to change
A Mars probe crashed when somebody mismatched metric and 'imperial' units in the software), an airliner had to make an emergency landing in an abandoned airstrip, this won the pilot an award, as he managed the no engine, gliding approach at a too high level, by sliding on the side. The reason of this commercial jet running out of fuel was a mismatch between fuel supply units.
They said also that USSR jet engines were more fuel thirsty than their counterparts, perhaps due to the lack of access to the rare elements used for high temperature and stress alloys, this limiting the efficiency of engines.
