If you control the speed of motors using PWM then you need PWM channels. I think 887 has 2 PWM channels but if all the 4 motors maintain same speed then you can use one or both PWM channels to control the speed, but if you need to have different speed for each motor then you need 4 PWM channels.
If PWM is needed then depending upon no. of PWM channels you need to decide the uC.
If you control the speed of motors using PWM then you need PWM channels. I think 887 has 2 PWM channels but if all the 4 motors maintain same speed then you can use one or both PWM channels to control the speed, but if you need to have different speed for each motor then you need 4 PWM channels.
If PWM is needed then depending upon no. of PWM channels you need to decide the uC.
It depends on whether you have a condition where the 4 motors run at different speeds. If yes, you need 4 PWM channels. If all motors maintain same speed all the time then one or two PWM channels is enough.
See the Fanout for the uC digital i/o pin. See how many digital inputs your one uC digital output pin can drive.