I am firmly of the view that MBA and SSC CGL can't be compared. The first one is an academic degree while the second one is a competitive examination for Government job at middle level. It is upto your academic inclination, your financial background and your preparation level for SSC CGL to take a decision in this regard. If you are genuinely interested to pursue MBA, you must try to get admission in a really good b-school after clearing CAT or other entrance examination. I would advise you not to join any third-grade b-school mushrooming everywhere in India and waste your money, time and energy. If you want to appear in SSC CGL, don't appear for the sake of appearing. Prepare yourself thoroughly, participate in various mock tests, try to judge your position and then appear in the examination. Here your target should be to get selected for the Govt. job at the first attempt.
Take decision after introspection and thorough discussion with your parents and relatives. However, please remember that you can always appear for SSC CGL even while continuing your MBA. In that case, if you are selected, you have to discontinue your study or postpone your joining Govt. There is a provision of delaying joining the selected post upto one year.
Beware! I question everything and everybody.