IIM

Hi There, There is absolutely no comparison between CAT and MAT
1. CAT is far more better than MAT as it is conducted by IIM and it is the only exam that if you crack, can give you a ticket to IIM while MAT is the least rated amongst all the entrance exams and is accepted by only low and average ranked colleges which would hardly give you any placement
2. CAT is conducted once in an year while MAT is conducted 4 times an year
If you are to take my advice, I would suggest you start preparing for CAT. Also do take up XAT and CMAT. XAT is accepted by Xaviers
3. CAT is accepted by all the colleges while MAT is only accepted by TIER 3 colleges.

For IIM, CAT score is important, and graduation needs only 50%, and for IIT:
Minimum 75% aggregate marks should have been secured in 12th standard (or equivalent) examination. The candidates should be within the top 20 category percentile of the qualifying examination. While calculating aggregate marks, the candidates should take into account scores of Physics, Chemistry, Mathematics, Language and any one other subject. The candidates will have to satisfy at least one of the following two criteria for admission to IITs: The candidate should have passed 10+2 or equivalent examination with an aggregate of at least 75% marks. For SC/ ST and BC candidates, there is a relaxation of 10% as they need the aggregate of minimum 65% marks. HOPE THIS HELPS, WISH YOU LUCK FOR YOUR FUTURE ENDEAVORS!