Part of what the Soviets tried to do was intimidate others. They wanted the world to know that they had the best military industry in the world. They made it clear that they would stop at nothing to control the world. Even though the Finnish outsmarted them, the Russians still made their point.
Yes, the Soviet's mission can still be considered a success when accounting for the total amount of damages incurred on the Finnish as a consequence of heavy bombings. Although, the Finnish were able to eventually outsmart the Soviet's, the city had already been destroyed and many lives had been lost.
I believe that he Soviet Mission was not a success. This is because they were actually outsmart by the Finnish. They could have done better than this since i believe that the Soviet Bombers are actually more stronger than they proved during this mission. Therefore, the mission was not a success.
I do not know much about this conflict but I would guess the bombers' mission from the Soviet Union was not a success if they were outsmarted by the army or planes from Finland. It looks like casualties can not be measured reliably. In the long run the Soviets did force the Finns to the peace table o it would most likely depend on the perspective.