Bsc computer science deals with the theories of the computer science. The lab part is a bit less and there is no provision of industrial training. The course duration is only 3 years.

Btech cse is more application oriented. The lab hours are more and you have to do internship in companies. The course duration is 4 years and you will be getting a technical degree after the completion.

I would suggest you to go for btech in cse as engineering is more application and development oriented.