Don't forget about different types of intelligence. There's sharpness, memory, puzzle solving, and so much more - someone could be extremely high in one category and abysmal in another.
But what seems to trump them all is emotional intelligence, which has almost next to nothing to do with normal intelligence? Or rather, has more to do with being raised by parents and oneself, I think bc wisdom (e.g. a willingness to learn from others' mistakes) has little to do with intelligence (the ability to spot mistakes on one's own, not necessarily coupled with a willingness to do so though).
Bc of all this, it's not so easy to simply judge someone as being "smarter" or "dumber". Though if they are making an extremely obvious mistake, or say something that took you a decade to puzzle out, then there's that evidence to go on - sometimes the other person makes it very easy to see who they are, at least in that moment, in that specific sense of intelligence.