An advantage to steel-manning an opponent (arguing against the best version of their argument) is that you get to see if they agree with your steel-man. This leads to many possible outcomes, and almost all are good for information within the debate. If the person disagrees with your steel man, they may rephrase their argument in a stronger way than your steel man, which may convince you of their position and cause you to change your mind. If they agree, you know exactly what you have to argue against.
There is some nuance to this which is very useful in social situations. For example, if someone immediately agrees with a steel-man, in a rather suspicious way, you may be able to detect if the person is using sophistry to convince you of something. Some people just speak non-sense while trying to signal intelligence or group loyalty, and you can accidentally create a coherent argument where there was none initially.
To summarize, steel-man arguments often lead to good outcomes:
(1) You may change your mind for good reasons
(2) You can find a clear path to argue with minimal semantic issues and confrontation
(3) You may identify motivated reasoners faster
http://lifehacker.com/utilize-the-steel-man-tactic-to-argue-more-effectivel-1632402742
An advantage to steel-manning an opponent (arguing against the best version of their argument) is that you get to see if they agree with your steel-man. This leads to many possible outcomes, and almost all are good for information within the debate. If the person disagrees with your steel man, they may rephrase their argument in a stronger way than your steel man, which may convince you of their position and cause you to change your mind. If they agree, you know exactly what you have to argue against.
There is some nuance to this which is very useful in social situations. For example, if someone immediately agrees with a steel-man, in a rather suspicious way, you may be able to detect if the person is using sophistry to convince you of something. Some people just speak non-sense while trying to signal intelligence or group loyalty, and you can accidentally create a coherent argument where there was none initially.
To summarize, steel-man arguments often lead to good outcomes: (1) You may change your mind for good reasons (2) You can find a clear path to argue with minimal semantic issues and confrontation (3) You may identify motivated reasoners faster