You are finishing your BTech and have to choose between Bank or CAT exams. You say anything is fine and prefer a Government Job. Many choose a Government job for its security, associated benefits, and pensions etc. The actual job you do may not be in sync with what you like or what you have studied.
The further course of action would depend on your ability to pursue higher studies, affordability and family commitments. If finance and time are at a premium and who have commitments, then go ahead with the Bank exams or CAT and get a job first. Then you can choose to continue education by distance mode from IGNOU or UGC recognized universities that would enable you to be prepared for promotions and career progression.
If time is on hand and finance is not an issue, the go ahead with M.Tech and then you would be better equipped for jobs in the private or public sector companies.Once you finish your M.TEch you can consider CSIR/UGC NET tests that would make you eligible for a good job.
The IBPS or Bank Probationary Officer exam for various banks need a fair degree of accuracy and speed to have a good score. It focusses on the ability to reason, a grasp for numbers, data analysis and interpretation.
Many feel CAT exams is slightly more tougher than Bank exams and it needs speed, command over language and analysis.
I would say spend some time trying to see the model papers and get a hang of Bank and CAT exams, So that you can choose either one of them> But it needs dedication, hard work and practice, many times.