Having lived in both cities, Delhi University is much better. Even the people of Mumbai have no second thoughts about that.
DU offers a wide range of subjects which aren’t there in MU. MU doesn’t even have a course in economics except Xavier’s. (Xavier’s Mumbai is autonomous)
The course structure of most courses in DU is well framed, which I don’t think is in Mumbai. DU offers a lot more of co-curricular activities as opposed to MU. It has more events too.
The infrastructure of MU is literally nothing as compared to DU. Most colleges like H.R., Jai Hind are located in narrow lanes and are just stand alone, old looking buildings. DU colleges are huge buildings and have great infrastructure. (Same applies to schools of both cities)
Infrastructure of Delhi is much better than Mumbai too. Local trains are well connected but requires great skills. Delhi Metro are well developed, clean and maintained. They are convenient and easy to use.
Food is muchhhh better in Delhi. Mumbai street food is typically pani puri, vada/samosa pav and pav bhaji. Food in Delhi is delicious and unlimited option wise.