Bitcoin, although gold is also a good option for investment, but btc is the future. It is volatile, but still it is trustworthy. After a few years I would be different person owing these btcs.
BTC is the virtual future based on technology. Gold will still be there whether you burn, throw, eat, mine or save it. It's still going to exist and will always be the best one. Between the two, Gold is much better for long term investments.