There is not much difference when we talk about the course and the subjects but the environment is significantly different for both. Here are some things that you should know about the institutes. 

Freedom- MCC offers a lot of freedom to its students in the way they dress and express themselves as compared to Loyola. Even for attendance, it is not as strict as Loyola. Loyola asks its students to pay for condonation and then sit for an exam. 

Ragging- It is still very much prevalent at MCC and sometimes it crosses the healthy limit as well. On the other hand, ragging is very rare at Loyola.

Drug scene- MCC is infamous for its drug-related incidents. While enrolling their children, parents are quite worried about this. On the other hand, Loyola does not have such a problem.

Campus- Both the campuses are extremely beautiful with an amazing experience of studying in the college.

College life- When it comes to cultural and extracurricular activities, MCC is more active as compared to Loyola. They conduct a lot of fests and different events which offer its students a lot of opportunities.

Here is a brief overview of the institutes. 

Therefore, it depends completely on what you want out of your college. If you want a good college life then you should opt for MCC. But if you want good academics then you should opt for Loyola. MCC has a diversified culture whereas Loyola has students mostly from Chennai.