As I have been a part of both universities I will give my two cents to your question as well.
I pursued my Bachelors from DU. I was very lucky in that I was a part of LSR and therefore my experience was a lot different from many others in DU who did not go to those top 10 name colleges. The Bachelors programme was great, there is a lot of exposure in terms of meeting people and the extra curricular is amazing. That being said – there is a serious issue with hostel, the examination process is outdated and the university is not very student friendly (especially when compared to JNU). The biggest issue I think most people face is the hostel issue. PGs are superbly expensive. I got bored by the time my three years were over
I did my Masters and am presently pursuing my MPhil from JNU. JNU is a lot tougher to get through in most ways because no one can predict what the university really is looking for. JNU has a lot of problems but it is in most ways an extremely accepting environment. It really does depend on what you do with your time in JNU. If you are motivated, you can achieve absolutely anything. There is a general culture of debate in the university which makes it so much more student friendly. It is an extremely cheap university and at least my department (IR/POLITICS – SIS ) was extremely rewarding in terms of faculty. It is difficult to leave JNU once you are in. It does promote a certain feeling of lethargy though if you are lazy because it expects you to push yourself especially at higher levels of study.
I think I was lucky because if I had the freedom that JNU offers at a younger age I would not have been able to handle it. Also. the BA courses at DU are of much higher standards in most respects (mostly because JNU barely offers any BA courses). That being said, the draconian rules and lifestyle of DU would not have suited me at all if I was still studying there. Take your pick. Ultimately it is what you make of the university that counts.