The difference is not 2-3 marks as you point out. It is 10-20%.
If you say that a poor man living in rural area doesnot have facility to compete, then why favour resrvation? Why dont ask the government to give this poor some money so that he can also compete? That shouldnt be based on 'caste'. It should be based on poverty.
Even in the case of poor, they should be given money to support, not 'marks'.