Thanks @stellabelle,
No leaving it in just Steem is not wise because it yields not interest and inflates over time. However, you will get half of your reward in Steem Power and half in Steem dollar anyways (see post). So the only decision you have to make is if you want to:

1. Hold Your Steem Dollar
2. Convert Steem Dollar to USD (my post shows this in detail)
3. Convert Your Steem Dollar to Steem Power

Steem Power is a long term investment and has various financial advantages if you believe that Steem will succeed in the next 2 years. Among other things with a lot of Steem Power you will get high interest rate and your votes will yield a high curate reward. However it can only be retrieved in 104 payments over 2 years as Steem. So it has a low liquidity.

Steem Dollar can be converted back to Steem almost instantly (using internal market) and thus provide much more liquidity.