Can you explain what you mean by SRC versus PVM speed control?
A touch of dyslexia seems to have crept in here. SCR (Silicone Controlled Rectifier) vs PWM (Pulse Width Modulated). Basically, an SCR controller clips the voltage to regulate the speed. A PWM controller supplies full voltage, but in pulses, with the duty cycle varied to control the speed. Since the torque is directly proportional to the voltage, the PWM controller provides better torque at low speed. Also, motors powered by PWM tend to run smoother, quieter and cooler because the frequency is upwards of 15,000 hz, whereas the SCR controller is clipping the standard 60 hz supply voltage.
I don't know which they are using, but SCR controllers are a lot cheaper.