Mechanics

All branches are good, the word better is mere perception of an individual. For one Civil may be good for the other EEE and vice versa. I can tell you the current scenario which may be helpful in developing your perception. India is a developing nation with lots of infrastructure development, population growth and global warming in the years to come, there will always be a need for Structural Engineer, Transportation Engineer, Water Resource Engineer and Environment Engineer. And all these fall under the category of Civil Engineers. EEE stands for Electrical & Electronics Engineering. This branch of Engineering has recently gained momentum due to the industrial demands of having an individual with skill set of both an Electrical as well as an Electronics Engineer. But to clarify Electrical Engineering is the mother of all these branches (ECE, EEE, EI, CS IT). This branch may make you work in State Electricity Boards, make you a professor with suitable specialisation, make you do research and sell new technologies (thanks to booming renewable energy sector in the years to come) or make you shift to an IT field job if you loose interest during the course of four years easily. Satisfaction - It depends on personal thinking. But the life of civil engineer is spent mostly at construction site. This is obvious because after a structure gets built there is no work remaining for them. So be ready to work under sunlight, dust, helmet on your head, dealing with contractors, remote sites away from city. You will not get to enjoy day to day corporate life as experienced by IT people. On other hand, being a mechanical engineer you have lot of options to work in. Right from IT company to construction company to heavy machinery builders. So indirectly you have options to choose from. Now a days you must have seen mechanical engineers are becoming IT professionals as they just have to get there hands on programming skill and algorithm development. So think wisely and good luck.

A diploma holder can join B.Tech course (regular or distance) by D2D process after completing Diploma in Engineering. B.Tech program allows Diploma students to take entry directly into second year of engineering course.
For taking admission in B.Tech, you must have done at least 3 years diploma after 10th in any branch of engineering.
Some colleges take admission through lateral entry exams like Joint Entrance Examination of lateral Entry (JELET), Diploma to Degree Entrance Competitive exam, etc. so you need to appear and crack these exams. Some colleges conducted their own entrance exam for getting entry.
Admission procedure varies from college to college. So you will have to contact colleges individually.