If nothing else, it's a good way to present to both of the children that their sole identity shouldn't be "the smartest one". DD8 was de-throned a bit when DD6 was tested and I hadn't realized she had seemed to have labelled herself "she who is most smart and is never wrong or challenged".
In a way, we had reinforced this image without even realizing it. I'll pass some of the blame over to the school, though, she had solid reinforcement of that all day!
I'm glad I caught this when she was young, though. It can lead to perfectionism and a host of other problematic issues.
I'm not going to pretend they aren't smart, nor will I minimize how different they are when it's an issue that is relative based on time and place. But I sure hope they realize how special they are in all the other ways they are special.
They are competitive, that's an issue I will never be able to fully resolve for them. I like to try and balance it by encouraging them to support each other in all sorts of endeavors. Hope this makes sense and is helpful.