First and foremost you should be really sure about pursuing CA after 12th. You should know the time you have to sacrifice and the level of accountancy and understanding involved. After that you should think about anything else.

Now when you're sure about pursuing CA, keeping IP MAT or DU JAT as back up will not be useful. WHY? Because when you'll study through IPMAT you will pursue BBA+MBA through IIM Indore, then if you'll study through DU JAT you will pursue BMS, BBE or BBA(FIA). All these courses require immense time and understanding of concepts which sometimes make it difficult for the students to cope with their CA.

Rather than these deadly options, students pursuing CA take admission in B.Com or B.com (Hons) course generally in a DU college. This helps students to cope and also provides them some knowledge about their CA.

Now why preferably DU? Because of flexible timings and no BIG attendance issue which really compliments the students studying period and favours them.

BUT if you're not sure about pursuing CA or want to try it on a like more of a trial basis PLEASE keep IPMAT and DUJAT as your back up exams as these are one of the best in the field of commerce.

All the best.