I suggest bitcoin because it's secure and fast no need to type any personal info and the transactions are totally free and if you save lots and lots of bitcoins right now you could be a millionaire after 10 years because more people are investing to this crypto currency more countries are starting to use bitcoin.
All well and good until you try to cash out.
How exactly do you intend to convert $1 million in bitcoin to cash without giving out all your personal info.
I make the argument that it's good to own both precious metals and bitcoin, but you would convert $1 million in bitcoin to cash the same way you would any precious metals. You do it out in the open giving your personal information away, or you do it the shady way. I don't see how the same doesn't apply to precious metals.