In my opinion, best investment for bitcoin is Cloud Mining..
Most cloud mining services turn out to be ponzi schemes, It's honestly not a very good idea to use cloud mining when there are other better options out there.
the main problem i can see with them, is that you need to trade to reach roi, you need to sell at some point your miner, so in the end it's not a cloud mining anymore
it's more like trading with hash instead with coins, therefore if you're not a good traders it's better to avoid