We must at least admit that Bitcoin is very young, and therefore any investments in are highly speculative.
Gold we know must go up, as it has proven to adhere to the fundamentals of money for thousands of years. With the amount of fiat currency inflation occurring around the world, gold will behave in a very predictable way. It has a track record that cannot be ignored.
That's not to say that the Bitcoin will behave differently, but it is certainly more prone to unknown risk - a virus, a hacker, manipulation (even a poor billionaire could do this right now), etc.
Any manipulation a billionaire or a millionaire could do would drive the price up. Pump and dump and getting rich doing so does not work by only suggesting a bubble by buying some bitcoins. You would have to also announce some services, get some names convinced the next big thing is around the corner etc.
Is Bitcoin really a risk? Who should destroy it? Governments still have a window of opportunity that is not closing for some months if not years to come but if govs really wanted to, why wait? The longer they wait the more businesses will get mad at them. Taking away our 300M$ toy is one thing. Taking away a 300G$ toy later is a different league although the Fed is printing this amount every 6 months.
Virus? Hacker? These are known issues that are a constant in the IT business. It's the same old arms race and the more we care about other people's wallets being secure the smaller the rewards will be for hackers and less attractive the bitcoin will be for them.