Well the F-86 also benefitted more from German help, the Americans possessing some of Germany's top engineers. The Soviets had also captured German engineers scientists, but they're production couldn't manufacture the advanced German designs and so compromises had to be made. The Soviets always thought of quantity over quality.
The western production technology was better suited for the advanced technology captured in Germany.
The Sabre design did for example take advantage of many of the inventions on the Me-262, such as the full span slats vastly improving turn performance, stalling and landing characteristics, z variable incidence horizontal stabilizer etc etc.
The MIG-15 featured wing fences to combat tip stalls, not the ideal solution but cheaper, quicker less complicated to manufacture.