You should take it because it’s interesting, your student would enjoy it, and you’d learn research skills.
You shouldn’t take it because you think top schools want you to. In fact, forgetting top schools, even lesser schools either don’t reward it or only give you elective credit.
it’s not mainstream and from both a top LAC my daughter got into and the lesser public my kid goes to, Seminar and Research had zero impact.
In regards to difficulty - I think it depends on the teacher but also the student’s aptitude to the subject.
It was my student’s favorite two classes in HS.
But in regards to impacting college admission or being rewarded when there- zero. My daughter’s school gave the same credit she got for English - so was wasted.
Good luck.