Sync just syncs but it doesn't prevent anything from starting to write while you go to pull it.
"udisksctl power-off" checks nothing is using the drive, commits buffers to storage, deconfigures the drive, and powers it off. Unfortunately it may kill more devices than you want in some scenarios due to the way killing the port works. Also for normal USB drives I don't think® poweroff is any different than an immediate physical pull post unmounting. The upside is it'll be completely disabled the instance the command completes, i.e. it can't even be written to raw as it is no longer powered even though plugged in. Not sure how helpful that is in reality though.
I usually just umount the drive which syncs and prevents further writes (well, to the mount at least) but doesn't try to kill it for me. Most likely sync is "good enough" for the vast majority of use though.
Eject is supposed to be like the udisksctl option but I've had it act wonky on me depending on the type of drive being ejected so I've avoided it myself. If it works though it shouldn't be any different.
"udisksctl power-off" checks nothing is using the drive, commits buffers to storage, deconfigures the drive, and powers it off. Unfortunately it may kill more devices than you want in some scenarios due to the way killing the port works. Also for normal USB drives I don't think® poweroff is any different than an immediate physical pull post unmounting. The upside is it'll be completely disabled the instance the command completes, i.e. it can't even be written to raw as it is no longer powered even though plugged in. Not sure how helpful that is in reality though.
I usually just umount the drive which syncs and prevents further writes (well, to the mount at least) but doesn't try to kill it for me. Most likely sync is "good enough" for the vast majority of use though.