Motor rated 7.6AMPS. How will motor behave if driven with PWM controller with 4A output?
The controller rated at 4 amps won't be suitable for your motor.  You shouldn't attempt to overload this smaller controller, unless you have a lot of in depth knowledge of motors and controllers. 

The direct answer is : the cheaper (4 amp) controller will fail with your load if you try to use the motor at full load.