"kata" is usually used to call senior person or person who you respect or stranger.
I'll give you some example
In party, you ask your boss "Who is she over there?(she looks like person who have authority of company)"
= あちらにいるかたは誰ですか?=achira ni iru kata ha dare desuka?
2. when you introduce someone who is very important for you "she is Ms.Mika from NY"
=こちらにいるかたはNYからきたミカさんです。=kochira ni iru kata ha NY kara kita Mika san desu
so, "kata" include meaning, respect or esteem=very formal
but "hito" just mean person
for instance, in class, you find new face. then you ask your friend "who is she?"
=あの女の人だれ?=ano onna no hito dare?
i think if you use "kata", people would not be offended, but this way is very formal. so it is not common in ordinal life.
"hito" is more common
I'll give you more example
あの人だれ?=you ask your friend about stranger
この人はバカだ=you insult certain person directly and there are some friend around you. if there are only you and this person, you say "あなた(おまえ)はバカだ”
i hope you make out