Comparing the average CTC of IIT Delhi and IIM Ahmedabad we get:
Average CTC of IIT Delhi: INR 16 LPA
Average CTC of IIM Ahmedabad: INR 26 LPA
One gets into IIM Ahmedabad after gaining 2.5 years of work experience. Adding the 2 year PGP Program, he is likely to start earning after 4.5 years. Around this time, candidates of both IIM Ahmedabad and IIT Delhi will be earning almost the same amount.
The only advantage an IIM Ahmedabad student will have is its tag which will add value in the long run.