Is dual degree better or individually B.Tech is better?

If you are not really research oriented then dual degree won't be a good option, but many companies, especially in the core field, have requirements of dual degree graduates. You are getting 2 degrees and saving 1-year.

Entirely depends whether your aim is to opt for M.Tech or not, if you want to pursue M.Tech then a dual degree is beneficial, otherwise, B.Tech is good.