Military hardware in this instance as rated BEST during a particular conflict.
BEST of course a very subjective. In these two particular cases however I might think that judgment well warranted.
1. Soviet 130 mm gun M-46.
The M-46 saw extensive use by the NVA [North Vietnamese Army] in Vietnam War, especially at the siege of Khe Sanh. It was regarded by both sides as the best all-round field artillery of the Vietnam War.
2. British Avro Lancaster heavy bomber.
"Adolf Galland (commander of the Luftwaffe fighters) considered the Lancaster to be 'the best night bomber of the war'"
See also another You Tube Video. That Lancaster and crew on a night bombing run.
The M-46 gun that rating a consensus opinion. In the case of the Lancaster, when Adolph Galland speaks, we have a more reliable, objective and correct judgment?