Hi, 

Yes there is same entrance test for getting into both mbbs and bds. Even the procedure to get into these courses are the same. 

See the basis depend on your choice filling.. If u have put up colleges for both mbbs and bds dn depending upon ur marks and ur choice filling preferance u shall be alloted a seat in a college. 

Marks do play a factor. But its the only factor. 

The way you arrange and lock choices also determines ur selection. 

And again both the courses are equally good. Apply wisely. 

All the best