The Russians liked western planes as well because they had very good radios, the instruments were well made, the engines were well made and the gunsight and cockpit glass was good. Despite some of the types being not 1st line fighters.
As for the P-39 in the hands of the aces most got their kills in 1942-1944 when the Luftwaffe had more of a presence in the East. Like a lot of aircraft the pilots that were succesfull in them tended to like them...you see that a lot in wartime. Look at the Japanese aces talking of the virtues of the Ki-43 and the A6M series in WW2 even later in the war when they clearly were not first line types. Aces are a funny breed (all nations) they tended to make due with whatever you gave them in many ways it was the man and not the machine. In that vein there were a few in the VVS that could fight in the Airacobra and do it succesfully. That they chose to stay with the type in some cases is something that you did see in wartime I guess it was a feeling of confidence in that model.
As for the Yak series...especially anything prior to the Yak-9U I do not agree that they were all that much better than a P-39. The LA series clearly was...and late model Yaks sure, but they did not come along untill mid 1943-1944. Prior to that you have LaGGs, Yak-1s, Mig-3 ect none of them really any better than a P-39.
