I could easily be confused here (I'm not an expert at reading datasheets, nor at using the spidev package!), but both the Python 2 and 3 libraries include the line
spiADC.max_speed_hz = (4000000)
(4 MHz). However the datasheet for the MCP3202 gives maximum clock speeds of 0.9 MHz at V_DD=2.7V, and 1.8 MHz at V_DD=5.0V.
Certainly I'm getting much better results from the ADC side of the ADC DAC Pi if I reduce this max speed setting.