which is better
My philosophy is to firstly make sure that you don't select something so ridiculous that it hinders your play (too high or too low), then pick a sensitivity that you enjoy playing/aim training with
For example if you enjoy playing with low sens more, chances are you will play more games and improve faster
if you're not sure which you would enjoy playing with more, consider finding a pro who's highlights you enjoy watching, then copy their sens and try to aim like them