The performance and function is the same for both Mini and 1.4 (also Ninja) Controllers, with minor differences in button controls
Other than the physical size, the significant difference between the Mini and 1.4 Digital Controller is how power to the heater is controlled:
The Mini Controller powers the heater as an on/off state
The 1.4 (and Ninja) Controller powers the heater with variable wattage, like a dimmer switch
This difference of power to the heater affects the lifespan of the heater; the variable wattage of the 1.4 is expected to preserve the heater's lifespan.
Both Controllers have the same performance, the 1.4 has superior components that will preserve heater function over time
Also, 1.4 features a 10amp power outlet on the back (so multiple controllers can plug into 1 wall outlet)