So the difference is that if you succeed they can punch you and if you fail they can ignore you?
You do know that you can apply some GM discretion what's appropriate and what's not.
If two PCs wants to buy a nice gun, but he shopkeeper say "It's not for sale, I only sell to members of the Jackass Gangbangers". The PCs try to manipulate the shopkeeper to change his mind. If they succeed, the shopkeeper has a choice, either to sell the gun to them for a fair price or to threw them out of the shop. If the players fail, then the only way they can get the gun is to take it. In this example a success can go either way, depending on if the shopkeeper has a guard or not.
A player is accused for murder and is sent to the tribunal. There he tried to defend himself by trying to manipulate the tribunal (by claiming self defense). If he succeed, the tribunal must free him or pick a fight. Fight is very inappropriate in this situation so that will not be an option. If he fails, then he will be sentenced for murder.
In both these examples it is the GM who is playing the shopkeeper and the tribunal judges. The GM simply has to go for what is logical for the situation.