Dude - you'll gonna be a management professional in near future,so please don't ask questions like "who's is better - Newton or Einstein"..."Bill Gates or Steve Jobs"
As for MBA admission tests - it's up to you! From where you'd like to do your MBA, where you'd like to settle down immediately post-MBA etc.
If you want to go into IIMs or other top b-schools in India and have just graduated from college or have insignificant(re few months/a year or so) WE then go for CAT. If you want to do MBA abroad and have significant WE(3-4 years at least with strong leadership activities both at job and outside job-place) then go for GMAT (although if ISB in your list then you still can give GMAT with low WE).
As for prep centers in Bangalore - not know in detail as I'm not based over there. But heard that jamboree works good for some people.
You may also want to explore the options
here in our club but before that go through
this.
Hope it helps somewhat and Welcome to the GMAT Club