If you are afraid to take risks of investing that money, keeping $15,000 will be a wise decision. But if you just keep it, it means you don't invest that money. If you want to invest that money, you must choose the option of number 1. Both have the advantage and disadvantage, it depends on us to choose which option that is suitable with our condition. IMO, if we have no proper capability in investment sector, it will be too risky to invest $15,000. But if we know well how to invest in a certain thing and we are pretty sure to gain profits, investing $15,000 should be an interesting way.
Funds always need to be diversified, and some part should be as a reserve for unforeseen situations, which we will not invest, but it will always be available to us 24/7. And the remaining funds should be invested only if you are confident that this investment will bring you profit and you understand what you are doing. If this is some kind of investment on someone's advice, then I would avoid it. Also, if anyone wants to buy Bitcoin now, then I would probably say that the best time for this has already passed, most likely you can still get x2 or even x3, but is this such a good profit when we are talking about high-risk investments?