Thanks for all infos @OmegaStarScream, really useful!
I believe that paper wallets are the most secure way to store bitcoins if you have big amounts and want to hold it for a good time also you can make 1 wallet for every bitcoin for example and have more security.
Paper wallets are easier to get damaged, and won't show if tampered with. The best way is probably with DIY physical bitcoins, with a QR code. Those have holograms which show if tampered with, and stand better against water.