Both the courses are good in their own way. But as compare to BDS, MBBS is much better than it. But it's depend upon the students choice. I think doing MBBS from foreign is better rather than doing BDS in Tamil Nadu

Dharani,

            The choice depends on a few factors:

• Career Interest: If you want to be a dentist, then you should go for BDS. Otherwise, if you have an interest in medical, you should definitely choose MBBS.
• University: The "foreign" should not be the priority. It should be whether the university is better. If it is, then you should try for that.
  
• TOEFL/ IELTS Marks: It is a serious factor since you may not get a visa from few countries if you don't have any of these two. Although it partially depends on the recommendation of college.
  
• Economical Condition: You should have sufficient bank balance. Otherwise, you may not survive in some environments (If you're getting complete study-aid then too)
  

Regards