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.
if have one million dollar, investment not buy bitcoin and hold
is good you can open star up business, open online store, create new altcoin and more
if one million dollar only buy bitcoin is danger investment