So I went down this path recently for a completely different reason. I was trying to get the unlocks for Disney Infinity. But if you think about it, no one should ever sell their used MBs. There is a data on there that you do not want to let out.
Nope. No "sensitive" data on a MB.
Just to keep things as clear as possible-
There is no reservation info, or ticket info, or credit card info,
or FP+ info "put onto" a MagicBand.
A MagicBand just contains (and weakly "transmits") a unique serial number that is used to allow Disney to access the information that is stored in your MyDisneyExperience computer file.
So, even if you were to lose a MagicBand, the info stays locked in your file.
The MagicBand works like the combination to a locked safe, or a key to a locked door.
The MB, itself, is not the file of info or the container of the info.
The MB just
unlocks the file of info, allowing it to be accessed from your
MDE account when needed.