Hi Sweetjoy,
The price of both Steem and SBD does fluctuate quite a lot but they both have their unique value for Steemians.

When you say power up 50/50 i think you are referring to when you post? If so, yes 50/50 rewards of Steem and SBD is usually the best option.

When I mentioned Powering Up earlier, I meant sending Steem from an external wallet or exchange to your Steemit account. Here is a great video by @joshdomsky on How To Power Up

Keep well :D