I would go for STEEM power or STEEM. Steem dollars are meant to be 1 dollar and I dont expect the price to go up very much in the feature while STEEM probably will go up much. If you use STEEM power your votes are worth more but if you buy STEEM its easier to sell and make profit when the price goes up.
RE: Investing more in Steemit: what kind of Steem should I buy?