The striations, along with the serial number exclusive to each set of three, are used to identify the different boules during the game.
Pointers prefer boules with striations:
• they have better adherence on difficult ground
• it is easier to put a spin on them
Shooters, on the other hand, prefer smooth boules which do not adhere to the hand and are released more easily.
After that, it's all down to "feeling" and personal taste !