my cryptocurrency - to trade SD to ST, use Market? or sell to Blocktrades?

I am a Steemit beginner, 2 week-old ^^. Actually, I got the reward for 1 week-worth.

Thank you for all my followers and upvoting!

Most of them advised me to increase Steem Power and I found out able to get by exchanging with Steem Dollar.

There are 3 options,
Market / convert to Steem / sell to Blocktrade

I put aside "Convert to Steem", it takes up to 1 week, Nobody recommend.

Another 2 ways show a little different ratio,
at present,
10 Steem Dollar is 6.044 SP at Blocktrades and 6.25 at Market.

Blcoktrades

Market