Steem.
Don't buy SBD. SBD are suppose to be a stable currency pegged to the USD. SBD currently sites at around 2USD but are suppose to be worth around 1USD and be stable at that price.
If you want to invest in Steem you need to buy Steem.
Disclaimer: this isn't a financial advice and I don't advocate investing in Steem if you haven't done your research.
You might want to take a look at a post I've made which reached the top of the trending page back when I posted it.
Yes, you are correct when the price of SBD is high.
However, when the price of SBD is close to or at $1.00, then it can be used a "hedge". In a bear market when prices are going down, SBD can be somewhat of a safe place to store value as the bottom of SBD price is fixed at $1.00
I would like to point out that there is risk. The risk is if STEEM price goes too low, then it cannot support the SBD peg. There is a mechanism that is called a "hair cut" that helps prevent STEEM from going to that point. The hair cut would allow SBD to drop. From what I have read, the "hair cut" has never been implemented.