In your example you have:
Person A: Abortion is wrong.
Person B: Taking away the right to control one's own body is more wrong than abortion. Therefore abortion is not wrong.
The argument is fallacious because it is irrelevant. Abortion could still be wrong even if it were legal. Furthermore, even if we accept that it is somehow more wrong to take away one's right to control their own body than it is to abort a fetus, that does not mean that the latter is not still wrong.
A straw man argument, by contrast, happens when one debater reduces the argument of their opponent to a more simplistic (or extreme) version and then proceeds to argue against that version. In other words, a stronger argument is made into a weaker one and then attacked.
If I were to reformulate your example into an actual straw man, it might go like this:
Person A: While women have an undeniable right to control what goes on within(out) their own bodies, that does not mean that they have a right to kill other humans. Since a fetus is a human, abortion is wrong.
Person B: Abortion is not wrong. The government has no right to control how women live their lives or use their bodies.
The key distinction to be made here is that the straw man argument weakens the original argument in order to make it easier to attack, whereas the red herring derails the original argument in order to evade the direction in which it was headed.