After seeing the arguments in court and on TV, it all boils down to two things:
1- If the SC rules in favor of PDM, then everyone from now on will take the assembly proceedings and speaker rulings to court.
2- If the SC rules in favor of PTI/govt, then a speaker of any party can make up rules at the whim and dismiss a motion etc.
Both the arguments have their merit and demerits. For PDM, the argument that you cannot interfere in house business, but can interfere if a constitutional violation has taken place is valid IMO (I am not a lawyer).
For PTI, the argument that the speaker did not make up a rule at whim, and actually had something tangible in the form of the letter in front of him which served as proof, and made him sure that this was a conspiracy. Also valid.
So the SC does have a tough job here.