Aviation

Getting a Job after completing CPL depends on the present market needs.
Nowadays, airlines have started looking towards type rated candidates. Some airlines have also switched to training the candidates through their own cadet pilot programmes.
There are some airlines who actually hire candidates who have a commercial pilot license and the selection process includes:
1. Technical Exam
2. Compass Test
3. Interview
4. Medicals
5. Induction.
Some airline also put Psychometric test and group discussion, as a part of their selection procedure.
Others who look for candidates with Type Rating on certain fleet like Airbus or Boeing or ATR, for simulator check and interview followed by medicals.
You may target vacancies for CPL holders, which are comparatively less in numbers when compared to those of type rated pilots.
So, after CPL, you may have to go for type rating depending on which airline you are targeting and of course, the decision shall also be influenced by the current market.
So, extra expenses after CPL is of getting type rated on any particular fleet to get a job and that depends on the current market needs.

Both the profiles that you have mentioned here are way different from each other. There is nothing comparable between them. Hence, there are only and only difference.
Commercial Pilot flies the plane and does the operational duty for the airline whereas someone who has done B.Sc. Aviation might be working for any department as per the company requirements. It may be operations, ground handling, ramp duties, cargo, hub control, etc.
B.Sc Aviation is merely a graduation degree which allows you to call yourself a graduate and hence, eligible for any job that requires it's candidates to be a graduate.
And, on the other hand, Commercial Pilot Course is a professional training which helps you earn a Commercial Pilot License and hence, you qualify to apply as a pilot for any airline that is hiring fresh CPL pilots.
I hope the things are clear now!