The primitive difference between the QAM and QPSK is that the spectral width of QAM is narrower than the QPSK. Furthermore, the BER (Bit Error Rate) of the QAM is higher than the QPSK. … Comparison Chart. Basis for comparisonQAMQPSKPerformanceAverageBetterBit error rateHighLowDifference between QAM and QPSK (with Comparison Chart) techdifferences.com › difference-between-qam-and-qpsk