205/55-16 is the correct size.
Directional means the tread points only one way... it's designed to only rotate one direction. Performance tires are usually directional.
Directional Yokohama AVS ES100:
Non-directional Pirelli PZero Nero:
It doesn't necessarily mean the tire is better or worse, it's just design. It does prevent you from rotating tires side to side (but you can still rotate front to back).