MAT

It totally depends on your choice of institution you want to go in. In some colleges, they take you on the basis of your National Level Examination ( CAT/MAT ) score while on the other hand some institutes conduct their own entrance exam. However, General Eligibility for MBA includes :
1. Minimum aggregate score of 50% (45% in the case of the candidate belonging to reserved categories) in his/her graduation or degree exam from a recognised university.
2. Qualify an Entrance Examination like CAT/MAT/ XAT/CMAT etc. - Some of the universities conducts their own entrance exam too.
3. Qualify Personal Interview as conducted by different institutes. Top Institutes from where you can pursue MBA :
1. IIT Madras, Chennai
2. Lovely Professional University, Punjab
3. Xavier Labour Relations Institute, Jamshedpur
4 Nirma University, Ahmedabad
5. Kristu Jayanti College, Bangalore
6. NMIMS, Mumbai
7. ICFAI Business School, Hyderabad.

Hello Avinash,
Your questions answer is subjective to your preferences. If you are good at solving lot of easy problems quickly and little poor at solving difficult problems, go for MAT. If you take time solving problems, but you get them finally, CMATs pattern may be more suitable for. Let me elaborate
Both CMAT and MAT are aptitude tests for tier -2 or tier-3 business schools. They won't fetch you the best colleges. If you want the best go for CAT. MAT has five sections. Each section consisting of 40 questions. So you will get 200 questions to solve within 150 minutes. Although you are supposed to pass in all five sections, one section GENERAL KNOWLEDGE, is not considered for final marking. CMAT has four sections with 25 problems in each section and you get 180 minutes for solving them. MAT is taken four times a year. So, need not worry if you missed the last one, another ones already on the way ;)
CMAT is held once a year. So, you got to be attentive for the form release and submission dates.
Cheers!