Financially speaking, FMS Delhi is a better option. The fees are extremely low compared to most other B Schools. The low fees do not compromise the quality of education here. But the accommodation and other expenses are high in Delhi. So the best option is to get a hostel in DU. But if you are okay with below-average rooms then rooms are available near FMS in the Malka Ganj area. They cost around INR 4000-7000.
If you go for IIM Ahmedabad, the scholarships and student loans will help you a lot. They will cover your tuition and hostel fees and will have to just pay your personal expenses (10k-15k in PG). One won’t regret investing in IIM Ahmedabad in the long run. But the ultimate choice is yours.