Hi, Rocio!
Great questions!
At this point, Walt Disney World Guests who are selected to test MyMagic+ have the choice of suing a MagicBand or a card, and your choice really just comes down to personal preference. If you like the ease of having a MagicBand right there on your wrist (no fumbling in a wallet, purse or lanyard for a card), then I would choose this option.
According to a Frequently Asked Question regarding
My Disney Experience and FR technology, "Each MagicBand contains an HF Radio Frequency device and a transmitter which sends and receives RF signals through a small antenna inside the MagicBand and enables it to be detected at short-range touch points throughout Walt Disney World Resort. MagicBands can also be read by long-range readers located at Walt Disney World Resort used to deliver personalized experiences, as well as provide information that helps us improve the overall experience in our parks.
If you prefer, you may elect to use a card instead of a MagicBand. Cards contain a passive HF Radio Frequency chip and cannot be detected by the long-range readers."
Personal preference will have to be your deciding factor, Rocio; however, those MagicBands are so cool! (can you tell I love technology...and toys?)
Happy planning! Be sure to send more questions as you think of them, too; we love to help!