Downloading allows you to get the previous Tamagotchi you had back, while resetting starts your Tamagotchi over again at Generation 1. If you choose to RESET your Tamagotchi you will lose all your prior history including Gotchi points, items, souvenirs and friends lists. If you choose to DOWNLOAD your Tamagotchi it will begin from the last major event (waking up, growing, IR communication). Be sure to check the time after doing this and adjust it to the correct time.