First of all, I would focus on the major differences between B.Sc and B.Tech. B.SC focuses more on theoretical aspects whereas B.Tech focuses more on practical aspects. For example, consider any simple topic of sequence and series which you might have studied in class 11th or 12th. In B.Sc, you will be taught more about the derivations of sequence and series whereas, in B.Tech, you will be asked tricky questions on sequence and series, thus focussing more on the application part. Your application of concepts will be made stronger in B.Tech, according to the present and future industry needs whereas, in B.Sc, your learning and understanding of concepts will be made stronger, thus making you capable of doing research or making other people understand that topic.
Now coming to the point of job opportunities and placements, engineers have better job opportunities and salary packages as compared to B.Sc graduates. Doing B.Sc from India's top universities like DU could get you direct placements, but doing B.Sc from average colleges will not get you placements with good salary package. But if you do B.Sc and then go for higher studies such as Ph.D or in the research field after doing M.Sc, you are going to get a good salary. For example, professors in government universities have a basic pay of Rs 1,00,000 per month. Similarly, the research field offers ample scope. Going for higher studies after B.Sc is better than going for higher studies after B.Tech. B.E. from government colleges, even if they are not so good, will get you easily placed in companies such as Infosys with a salary package of around 3-5 lakhs (consider it to be the worst scenario). B.Tech from good government colleges can fetch you packages as high as 20 lakhs per annum but I won't suggest you do B.Tech from private colleges if you are thinking about placements since they will first get you placed in some company but later on, the company will shed you off.
There are some profits in going for B.Sc. You save one year, as well as B.Sc, has much lower fees as compared to B.E./B.Tech. If you are already thinking for higher studies or civil services
or bank jobs or research or such other opportunities, B.Sc is a good option.
Now, coming to the point that you are thinking to drop, I won't suggest this. There are few students who are able to improve their JEE Mains Rank, but there are rare students who can improve their rank by a significant number to get B.Tech Computer Science in a good college. So, you should take B.Tech in an average government college (I won't suggest a private college for B.Tech), or go for B.Sc Computer Science.