The choice between BBA or B Com solely depends upon your inclination, aptitude, and passion. Each is a 3-year course after 12th and offers multiple career choices. Generally, people who want to pursue B.Com want to be hardcore financial number crunchers, they are people generally devoted to finance and even if they pursue MBA after B.Com they generally choose finance as their area of specialization. Besides doing MBA, they can also choose to do M.Com, CA, ICWA. They can also join jobs in the accounts department of companies, or they can also work with banks and finance and tax consultants.
BBA course is a more comprehensive course which aims to better equip the student with other aspects of business besides finance like Human Resource, Marketing, Operations, and Systems. BBA courses are industry-tailored courses aimed at equipping the student with requisite managerial skills.
Students who graduate in BBA can pursue their post-graduation only in MBA; alternatively, they can also seek employment in companies as management trainees. Some people may also decide to pursue part-time MBA while working. As a BBA graduate, you can seek to specialize in finance as well as streams other than finance such as HR, Operations, Productions, Materials Management, Marketing, and Systems.
To Sum Up, Choice, of Course, depends on:
Aptitude of student
Score of student in entrance
College reputation
Career prospects
Opportunities
Constraints
It is advisable not to think of how much money you will be able to make but carefully analyze your interests and aptitudes before choosing an alternative and then steadily work towards honing your aptitude and skills in your specific area of interest. From the broader approach, the narrower and reach your pinnacle. Top notch institutes for are IIM-Indore, Shri Narsee Monjee College of Commerce and Economics, K. J Somaiya Mumbai, Lovely Professional University, Punjab, Delhi University, Christ University, Bangalore, M S Ramaiah University, Bangalore, Madras Christian College, Chennai, Mount Carmel College, Bangalore,Mumbai, Wilson College, Mumbai, Lala Lajpat Rai College of Communication & Economics, Mumbai.

You have done your 12 from science stream. Doing Bcom and BBA would be begining from scratch from you . These are management course different from wat you studied earlier.

Both course are not very different. Both include subject like Accounts Economics, Busniess law,... Basically all commerce subjects

Your admission depends on your marks in 12 standard. For Bcom you can get admission in Du with a cutoff of between 85-99%.

Other than Du you can fill application form of different universities. Like Ipcet, they take entrance and need 50% in 12.