Hi there

In regards to your question the basic difference between both of the educational fields is that one belongs to the basic sciences field and other belongs to engineering sciences. Bsc. will prepare you to take up more and more research based opportunities in the future whereas in BTech you would be more encouraged towards practical applications and therefore the companies who recruit you would demand the application of concepts in their work. The salaries for both would really depend on the amount of skills you have developed in both these fields and the amount of experience you have. Also it depends on the university you're planning to do your degree from as they have significantly different statistics in freshers placements.

Hope this answer helps; best wishes