Safest way is to create a new wallet in your new device and transfer your coins to that wallet. A little more expensive now, when transfer fees are high, but if you don't have too many addresses it doesn't cost THAT much.
If you do this, then you do not need to worry, that the next owner of your machine could somehow be able to restore your wallet from your HD and spend your coins...
Safest, but not convenient, and most importantly costs you something when you can just go on and retrieve a backup from another device. In that case you'll lessen the hassle plus any expenses made on sending your balance to a new address would also be avoided. Though you need to maintain the integrity of your backup and keep it in a safe place i.e. thumb drive isolated from the internet/not being used or a machine that's not connected to the internet to avoid data loss.