Ive only used 195/55 in sic looooong ago...it was the potenza re711. Pretty good actually...though im sure a 195/50 wiuld be better due to the lower profile si will have lesser tire wall flex.
205/50 not sure. But the wider tire width will give more surface area for grip and the tire walls profile oso wont flex as much since its slightly lower than 195/55.
In the end, still comes down to tire brand n model....