Regarding Kim/Seo, I won't discuss about their technical abilities, as I don't think I'm qualified to judge that aspect.
However, there are two things I can observe that set them apart from other MD pairs.
The first is their mentality. Even under pressure, they can remain 1000% focused and consistent, especially against opponents who typically apply attacking style. Kim/Seo defends tightly like a great wall and patiently returning all the attacks they received, then looks for opportunities to counterattack or wait for their opponents to lose focus and patience and then make mistakes.
Kim is the missing puzzle Seo has needed all this time. Compared to his previous partners (Kang Min-hyuk and Choi Solgyu), Kim is relatively more stable and reliable.
This makes Seo feel more comfortable, he can focus on creating attacks, Kim is great at defending from the back and is tenacious at the net, something he didn't get from his previous partners.
The second is their ability to successfully evaluate their losses and then implement the right strategy, which is why they rarely experience consecutive losses to the same opponent.
In fact, so far, Kim/Seo haven't had an opponent who is consider as their kryptonite or antithesis.
Their playing style, which requires continuous endurance and high concentration, is the reason why they have experienced a few losses or marginal wins.
Who will be their next challenger?
I think the current top 5 MDs have all the weapons to defeat them in the conditions I described above (their physical condition is not there, or their opponent apply a new strategy that they have not anticipated) , but in the long term, perhaps the young Indonesian pair (Raymond/Indra) has the potential to become their new challenger.
