If you already own the cartridge (XCI) or a digital copy (NSP from the eShop), getting the update is simple:
Both work identically in terms of gameplay. The choice comes down to personal preference. However, NSP files are more common for "pikmin 4 switch nsp update" because updates and DLC are distributed as NSPs by default. pikmin 4 switch nsp xci update eshop free
With an official eShop copy, your 60-hour save file is automatically backed up to the cloud (with a Nintendo Switch Online subscription). If your console breaks or you buy an OLED model, your Pikmin progress is safe. A jailbroken Switch running XCI files cannot use cloud saves, and local save corruption is common. If you already own the cartridge (XCI) or