if you are migrating contents, go for disk cloning but make sure it supports 3TB.
ghost 1TB source to a 2TB is ok with most dual docks with disk cloning
ghost 2TB source to a 3TB is ok if your dual docks support 3TB and the 2TB must be in GPT, otherwise you cant extend the 2TB partition.
Anyways, I had 8 tries to get this right when i migrated my 1.5T/2.0T disks to 3TB