CAT is the entrance examination for admission to all the 20 IIMs. Now IIMs have an Academic Diversity Factor that is usually for Candidates who have taken up a different variety of courses than your regular and conventional B.Tech, BBA, courses. MBBS, CA Candidates usually get marks under this column for bringing Academic diversity to the table. Now these marks are usually 5-10. But when you are looking at admission to IIMs, even a mark does matter. So the variety you add to your profile works in your favour. So CA is a good option if you want to join IIMs. But if you are fine with any College, you might join BBA or even Integrated BBA+MBA.