This is a discussion on SB Preflop Play: Heads-Up vs 6-Max within the online poker forums, in the Learning Poker section; Why is it recommended to open-raise about 27% of hands from SB in 6-max, while the same range in heads-up is well above 50%? What
First, position. You have it heads up, you don't in 6-max. It makes a huge difference.
There's more to it, basically you need to play more to compensate for being in one of the blinds every hand. But, most of it is position. Consider the difference between what you should open UTG in 6-max and what you should open the button with. And, that is without having a discount and you need to get through 2 players.
Adjusting for the blind payment makes sense. However, the positional aspect still confuses me. When all other players have folded, sb is still out of position w.r.t. bb as exactly in the case of heads-up. sb acts first both in pre-flop and post-flop, and no one else is in the game except sb and bb. I just can't see the difference. What am I missing?
Heads up the button should post the small-blind and the big blind is posted by the player not on the button (which makes sense if you think about blinds as a method to encourage people to play out of position).
So, heads up, the small blind acts first, but they get to act last on every other street.