JECA is best for MCA in Kolkata. If you qualify this test with good rank then you can take the admission in best colleges like Jadavpur University, Calcutta University, kolyani University, these are very reputable colleges in Kolkata. But there are certain conditions to be fulfilled to take admission in Jadavpur University. These conditions are you must have at least 60 percent at 10th , 12th and graduation.
I would recommend you to take admission in these colleges because they have good placement record in their past performance.
You can participate in NIMCET also, if you aspire to get into the natinal institute of technology. But this examination held all over India. And it is little bit tougher then others examination. And competition is also higher, if you want to qualify this examination then you need strong determination and consistent hardwork.
Once you get a chance in nicet your life is totally changed.