The best approach is first to determine which one is better suited to your talents, and your desires. Changing majors in mid university is really deciding you don't want to do this as a career.
So, if you choose based on money, than it will be a job.
If you choose it because you have an aptitude for and more important you enjoy it, then it will be rewarding to your total well being.
Mechanical and Electrical really take different skills and aptitude.
Civil is more related to buildings and roads.
Computers have many offshoots and hardware, firmware, and software.
Computers are found in many devices outside of PC, tablets, and Phones. But if you are not interested in computers, or don't feel talented in them, then other majors might be more enticing and rewarding.
Rewards should focus on making you happy, as you will be doing these jobs for a long time.