The difference would be -1.3% in diameter for 195/50R16, +1.7% in diamter for 195/55R16. If wanted closed to original size, 195/50R16 would be better. If the number diameter difference too high eg. more than 2% it might affect the accuracy of speedometer.

Can use this website to check, just key in original size and look for alternative size:
https://tiresize.com/tyre-size-calculator/