Hi @dg93!
Steem fluctuates in value against other crypto such as Bitcoin and also fiat such US$ or Euro€. You can view it's historic price charts on coinmarketcap.com. Post payouts used to be in Steem. But recent changes now mean that payouts are in Steem Backed Dollars (SBD) and Steem Power.

SBD are tied to the price of the US$ more or less and see very little fluctuation of price. My guess is that this was done to ensure that the price of Steem never falls below the price of the US$. If the price of Steem does drop, what you see on the internal Steemit market is people then trading Steem for SBD, thereby preventing its value dropping any further.

Here is a price chart comparision between Steem and SBD.

Which is better to invest in, is a decision you will have to make by looking at the charts and making your own informed decision.