Like any liquid currency, it depends on what you're doing with it. I don't know that I'd be anxious to hold either Steem or SBDs as a cash part of my portfolio right now; there are other cryptocurrencies that seem like they're going to do better in that mode (EOS particularly, with its airdrop potential) in the near term.

Steem and SBD are great for actively investing, either by staking Steem or buying things with SBD. If they're sitting in your wallet without an intended purpose you're probably not making the best use of them.

That said, you're right that holding Steem is probably a better plan than holding SBD. There are a lot less SBD so they're still in a zone where pump-and-dump might happen, but there are so many other coins now to do that with it's very possible no one will ever hit SBD again.

Also, there's a significant faction of witnesses who want to take action to hold SBD at $1 USD if it ever gets there naturally. So there's a substantial chance that if it does fall that far it will never go back up.