Transferring your old Splatoon 2 save data into Splatoon 3 will grant you three — yes, you read that right, three — Gold Sheldon Licenses, so it is well worth the minimal effort.
Gold Sheldon Licenses are an invaluable asset in your early game. Instead of unlocking weapons as you level up, these rewards will let you unlock weapons instantly, way above your level grade, jumping to the skills that your hard-fought grind has earned.
On top of this, you will have the ability to get into Anarchy Battles straight away, start with a higher rank and get more accurate skill matching.