Which is the best campus of SRM after Kattankulathur campus?

I think you should go for Ramapuram campus. It comes second after Kattankulathur(Main Campus).It has better infrastructure and facilities as compared to Vadapalani Campus. Vadapalani campus is very small and there are no playgrounds or Auditoriums.But it has centralised AC in all the classrooms.And coming to the placements ,it does not matter from which campus you belong to. All the students will be called to the main campus for placements.
So your order of preference should be:
1.Kattankulathur Campus
2Ramapuram Campus
3.Vadapalani Campus
4.Ghaziabad (NCR) Campus