B.Tech is all about engineering. Which is best? Well that no one can say. My suggestion is that you check what you like. Do you like mechanical or chemical or electronics or computers, instrumentation? There are more specializations like civil which is all about buildings and structure broadly, electrical engineering. Actually one cant summarize an engineering course into one line. 

My suggestion - check each course of engineering. See where your interests lie because you will make a career out of it and that is for a lifetime.

As for scope, there is plenty. You become an engineer and work like one albeit in your specialization maybe. You can build that with an MBA or M.tech or go abroad, do research. Jobs can be in manafacturing industries, software firms, banking, civil services, defence and so on.