which is better btech or dual degree in mathematics and computing from iit delhi?

Why did higher rankers preffered btech over dual degree although its knew?

i could have easily got btech MnC in iit delhi but i ranked dual degree above it in preference?

was that a wrong/bad decision?

The question of better and bad is always a personal marking. The demand of the situation determines whether you should choose BTech or Dual Degree. If you want to be in academics you should choose Dual Degree because it will give you ample time to understand your field well or if you have some other goals like switching you should take Btech. And regarding the decision “Decisions are never right or wrong the hardwork put in afterwards makes it right or wrong”. Don’t be a crowd-follower Carve out your own path