Which college should I prefer for MCA if I score 70%-80% in BCA?

For MCA admission, the first preference is given to ranking in entrance exams i.e. PGCET or KMAT. There are some colleges offering MCA on merit basis. You can try in BITS. Else Pune or Bangalore is a good option.

Try to crack some Govt. universities first like: JNU IPU IIM-Indore, etc. Otherwise, you can get a good private college through a simple interview or entrance.