This question can be best answered by someone who has had a taste of both campuses. Fortunately one of my friends was lucky enough to move to IIM Ahmedabad after studying for a year at IIM Kozhikode. He shared his experience and the various things that contrasted in both the B Schools.
Faculty: Being the topmost B School, IIM Ahmedabad does attract some of the best faculties that are experts in their fields. They had too much knowledge and experience to impart making the classes a thrilling experience.
Crowd: While the crowd at almost all the good B Schools attracts only the best, IIM Ahmedabad is famous for its exceptionally good peer groups with only geniuses and masterminds in their respective fields.
Academic rigor: Normally B Schools offer a very hectic life with academic pressure combined with placements and clubs and committee activities. But at IIM Ahmedabad the topmost preference is Academics only. You are required to attend 3 lectures of 75 minutes of case study daily. These case studies are extremely lengthy and on average you are required to read 300 pages every day. Such economic rigor is lacking in the case of IIM Kozhikode.
There are several more minor differences between IIM Kozhikode and IIM Ahmedabad but these 3 are the main things an aspirant needs to consider while choosing one of the two B Schools.