The 195/55 has almost 1cm taller sidewall so 195/55 will be:
1. more comfortable, consequently slightly less responsive steering.
2. Bigger rolling diameter by almost 2cm so actual speed is higher than 195/50 for the same rpm.
3. Distance travelled will be slightly more
4. Heavier and theoretically slightly more fuel consumption.
5. Higher ground clearance by almost 1cm.
6. Reduce fender gaps by almost 1 cm.
Additionally 195/55 has more choices in the market.