Programming for Arduino Uno VS Latte Panda with Arduino Leonardo

Although I can't help with the Latte Panda, I can show you an easily readable snippet when the variable is ONLY 1 character via use of "switch case":

void loop() {
  if (Serial.available() > 0) {
      char val = Serial.read();
      switch (val){
        case 'S':
          digitalWrite(Direction1,LOW); digitalWrite(Speed1, 0); 
          digitalWrite(Direction2,LOW); digitalWrite(Speed2, 0);
          break;

        case 'M':
          int D1 = Serial.parseInt(); 
          int S1 = Serial.parseInt(); 
          int D2 = Serial.parseInt();  
          int S2 = Serial.parseInt();
          break;
      }
  }
}