I have read the question in details. You have stated that you don't want to 'do job' after B. Tech. Then what do you want to do? Are you planning to join faculty position? If this is the case, then you have to go for M.Tech in your specialisation, i.e., ECE.
On the other hand, MBA degree gives you managerial capability, which helps in the coporate world. MBA degree is almost essential for career progress in the corporate world or in PSU.
I feel that you don't have done any career planning. It is totally upto your future planning and academic inclination to decide which course is suitable for you-M.Tech or MBA.
Beware! I question everything and everybody.