MCA

Hi Pranjal,
As you know, both are different areas of study. MCA explore a gateway to IT Industry and you can find job as Application, Software Programmer, Web Programmer, Software tester, etc. while MBA is a key into corporate managerial life.
But you must know the structure of both programs. MBA is of two years in duration and the Duration of MCA is three years( Lateral Entry system into direct 2nd Year is available in some universities, but only BCA, B.Sc -CS / IT graduates can enjoy the benefit of LET).
MBA is almost the continuation of B Com degree as the subjects are similar such as Management, HR, Finance, Accountancy, Business Mathematics / QT, Corporate Laws, Business ethics, etc.
But MCA is entirely different in course contents / subjects. Being a technological PG, MCA, mainly deals with subjects like Computer Architecture, Database Management System, Various Programming Languages, Digital Electronics , Communication Technology, Web Programming and Development, Application Development , Cloud computing, Computer Oriented Numerical and Statistical Methods, Discrete Mathematics, etc. and many more.
Some Universities such as CUSAT, Calicut Universities in Kerala admits only BCA, B.Sc, B Tech graduates to their MCA Programs. But in most of the university, admissions are opened for graduates with mathematics at HSC level / graduate who had studied mathematics as a subject.
Think twice. As a B Com graduates, it's difficult to study technological subjects. Same thing is happening when technical graduates choose MBA. Still you are interested in MCA, Go ahead. You can win.

Devoting one full year for competitive exam preparation has its own merits and demerits. Dropping a year means that you will get sufficient amount of time to prepare for competitive exams. It will allow you take mock up test and help to score good ranking in competitive exams. However, one year is a long time so the possibility of you may change your goals and objectives. You may become lethargic because of availability of time and lesser pressure. You may waste time. If you are confident of keeping the momentum, dedication, determination, readiness to work on a plan, will to achieve your objective and support of family; you may consider dropping a year for competitive exams.