I think the fundamental difference lies in how they respond to insults or confrontations.
Sai's style is to go full throttle. She says everything she feels, she doesn't hold herself back. She doesn't mince her words and yes she sometimes gets a little carried away in the anger and in the flow. She is loud and in your face when she gets confrontational. Yesterday when she handled those ladies i thought she was spot on though. Neither too loud but her stern tone ensured that she was "heard". But Sai runs the risk of becoming so loud that all people remember is how rude she was and not focus on WHAT she is saying. Thats definitely a problem because Sai drops truth bombs and shows the mirror like no one else can.
Whereas Virat is usually the polar opposite. Whether it is the not so important confrontations in GC about Sai's dads VRS or big things like his marriage and today this Shivani bua issue, he always says very little and is far too measured amd too "polite and civil"in his responses. Today there were many points when ninad, bk, sonali, pp were talking that he clearly didn't agree with their thought process. He kept flinching or shaking his head disappointedly. Especially when BK said ki uske taange tod ke ghar par bithana tha. And sonali said ek besharam dusre ka saath de rahi hai. Ninad also had said ki Sai ne dhoke se shaadi ki. But he didn't "directly" respond to any of these things. He kinda let it slide. I mean from his gestures abd demeanor its clear he didn't agree but he didnt counter them line for line. He made his overall stance clear that he supports both bua and Sai but he didnt counter every single allegation. Like he did NOT say, no Sai didn't do any dhokha. Or no, shes not besharam. But because hes so calm in his confrontations his words lose their "sting and power," which is sometimes needed. People dont take him seriously enough because he is too "nice" . So he needs to learn to speak UP- literally- show his intention in his tone and choice of words. Yes its great he is respectful even when he disagrees but sometimes a "little bite" is needed.
For example Sai contines to face a lot of taunts but NO one has ever repeated a word directly about her aabaa after the reception incident. Because she was pitch perfect in that confrontation.
But Virat has never been as "stern". In the course of all the scenes he had stated that even though the shaadi was a result of consequences, it was HE who decided to marry Sai, not the other way round. He has said its not an ehsaan. He has said ki meri binti hai ki Sai ke saath bhi parivaar ke sadasya jaisa vyavhar kiya jai. But none of these things are actually happening because he is SO polite in his tone that peoole dont think their bad behavior to Sai will have any consequences.
It doesn't help that everyone except PP is older than him and also to Sai so even when he takes a stand in support of Sai against the elders, he never tells them to apologize to Sai for speaking rudely to her. He doesn't ever say- thst kaku/baba, apne abhi jo Sai ke baare main kaha, voh bahut galat hai aur aapko uski maafi maangni chahiye. When an older person makes a mistake they should also "apologize". When BK literally flung Sai's certificates he looked shocked but he tried to "pacify" her afterwards. He didnt ask her to apologize.
I think thats because he just cant exercise those rights in front of them.
But whenever Sai makes a mistake even though Virat tries to be patient with her, he really goes off on her. Haq jata kar he forces her to apologize and rectify the errors. Whether it was manaofying kaku in the reception or bringing PP back home. And Sai is probably the only person he has completely lost his cool with where he actually "scolds her loudly". He has done that quite a few times already. Some more serious than others. I think until this precap his behavior was the worst with Sai when he thought he was losing his job and he flung the plate of food and lost it with Sai.
Virat only seems to feel that haq on Sai. Maybe its coz shes the youngest and she is his wife so he feels he can take that liberty with her. Hum khul kar gussa unhi se kar paate hai jinse hum pyaar karte hai. So even before he realizes his love, this liberty he takes to really take out his gussa on her shows the apnapan he feels. But obviously there is a limit to it. He cannot be actively confrontational only with Sai and so passive in confrontations with the rest of his family.
And he cannot expect that Sai will undergo a U turn in her personality to approach all confrontations the way he expects or the way virat himself would. Her core nature and attitude cannot be completely replaced. Just like he wants her to tone it down, he should tone it up to compensate.
So basically virat and Sai need to borrow some pages from each others approaches to confontation.