Is it better to buy my magic band at the resort or park instead of the online
Disney Store which seems to have a limited selection? Is there a better selection? Similar prices? Would I need to charge it for a night before using it? Thanks!
If you don't have a resort reservation with Pre-arrival discount, OR you don't like the selection available for resort pre-arrival discount (which does change, so check back from time to time) in My Disney Experience, then you can purchase from Disney Store web site, Pin Traders at the Marketplace End of Disney Springs, various shops in the parks, or the resort gift shops.
The difference:
Pre-Arrival bands for resort stays, DVC or Annual Passholder via My Disney Experience come pre-linked and assigned to the guest, and their name engraved on the back. Usually you get a discount of up to $10 per band.
Bands purchased in-store, or Disney Store web site, must be linked and assigned to guests in My Disney Experience. The bands are sold at full price, unless they are having a sale, or you can use some other discount like Annual Passholder or Disney Visa at time of check out. There is often a wider selection available, especially at Pin Traders in Disney Springs or The Emporium at Magic Kingdom or the Dark Room at Hollywood Studios.
EDIT: I forgot to mention, in either case, you'll want to also charge the MagicBand+ before using its long range features (i.e. auto linking ride photos and videos on rides like Seven Dwarfs, Tron, Frozen, Guardians, etc. just any ride that doesn't have bank of monitors at the exit to tap and claim your pictures).
The bands should also be fully charged, then paired via Bluetooth to your phone and the My Disney App upon first use. This allows the band's software/firmware to get any updates to ensure it has the latest features and fixes.
To pair/link the bands to your phone, install the Disney World app on your phone, open it, sign in if/when prompted. From the app's main screen use the 3bar (aka hamburger) menu button, scroll to the Account section and select MagicBands & Cards. From the top, select the card that has "Your Name" and "Pair your MagicBand+". On the next Screen, for Pre-Arrival Discount bands scroll to find your band, once its in focus, scroll the screen a little and select the PAIR button and follow the prompts. For Store Purchased bands, use the "+Link" button and follow the prompts. Once the pairing/linking process is complete, if the band is in need of an update, you'll be notified, again just use the upgrade button and follow the prompts.
If you are linking store bought bands, be sure to be very careful and select the correct person. Once the band is assigned to someone it can't be re-assigned to another person.