What the choice actually controls
Strip away the prestige talk and the stream choice controls exactly one thing: eligibility. NEET wants biology. Engineering entrance wants physics and maths. CA Foundation and most commerce degrees are reached most naturally through Commerce. Law, journalism, psychology and the civil services are open from any stream, and strongest through Arts for the ones who read and write.
So the question is not "which stream is best" — no such stream exists. The question is "which exams might I want to sit in two years, and what do they demand". Everything else is decoration.
Choose backwards, not forwards
Most families choose forwards: pick the most respectable stream the marks allow, then see what it leads to. This is how students end up in PUC Science with no interest in any science career, grinding through two hard years to reach exams they do not want to sit.
Choosing backwards is calmer. Spend an evening on the career pages of this site and shortlist three or four endpoints worth wanting — a job you could imagine doing at thirty. Each pathway page names the stream and exam it needs. If your shortlist points three ways at once, pick the stream that keeps the most of it open. If it all points one way, the decision has made itself.
The honest case for each stream
Science is the widest road and the steepest. It keeps medicine, engineering, pure science, agriculture, pharmacy and more open — and it also permits almost every course the other streams lead to, which is why undecided strong students default to it. The price is two years of the board's hardest syllabus, usually alongside entrance coaching. Pay that price only if something behind the science wall is actually wanted.
Commerce is the road of money as a subject: accountancy, banking, business, economics. Its flagship — chartered accountancy — is among the hardest professional qualifications in the country, so nobody should call this the easy stream. It suits students who like numbers attached to the real world rather than to laboratories.
Arts is the reading and writing road: law, civil services, psychology, journalism, political science, history, design. It has the worst reputation and some of the best endpoints, a gap this site exists to correct. It suits students who argue, write and remember — and it leaves the door to the IAS exactly as open as any other stream does.
If the marks and the wish disagree
A student who wants science but scored poorly should ask why the score was poor. A bad year has remedies — Karnataka's board now holds additional exam sittings in the same year precisely so one bad day is not final. A genuine dislike of the subjects does not have remedies, and two more years of it will not create one.
And a student with a strong score who wants Arts or Commerce is not "wasting marks". Marks are not a currency that must be spent on the most expensive stream. They are evidence of a student who works — and that student will be near the top of whichever road they actually want to walk.