Personally (although I'm still a very small player !) I go for a blended approach. I tend to alternate between buying HBD and Hiver Power, mainly based on which one is a more attractive price at the time.

The only slight concern I have with HBD is my own lack of knowledge. I really don't understand where the money is coming from to pay such a great return. How would it be funded if a few external whales invest in HBD and then all want to cash out with their returns after a few months or years ?

As far as I can work out, the only actual revenue source HIVE has is from fiat people convert to HIVE or HBD; it doesn't sell a product, have advertising revenue or directly charge for a service. I adore Hive as a social platform and for the rest of the ecosystem, but I'm sure there's some piece of the jigsaw I'm missing that enables HBD to pay a 20% return rate.