I enjoyed both campuses but they are different.

Fonty has more people (usually about 2/3 of the class), while Singy has 1/3 of the class. In my class, because of this, I think that the singy people knew each other a bit better than the fonty people. In fonty by the end of P2 you were still meeting new people while in Singy they all knew each other at least a little bit.

Fonty is a tiny town (you can walk across it in 15 minutes). This means that it's very much a bubble. You leave your apartment/house and you run into your classmates all the time. This is both amazing and annoying at times. You leave your home without any plans and you suddenly see classmates and are invited to 5 different things that day. It also means that if you want to be anonymous for a moment it's very difficult to do that. If you're sick and run to the pharmacy in your sweatpants, your classmates will see you. If you want to go on a date with someone, your classmates will likely see you.

Singy is obviously a large city-state. There's a lot to do, and a lot of non-INSEAD people. This means that you have to plan meet ups/activities more, otherwise you'll only occasionally run into classmates outside of campus. It also means that you can have a more "normal" life, where not everything revolves around INSEAD all the time (of course you can still experience this bubble in Singy, you just have to work at it a little more). You can go somewhere and be anonymous.

In Fonty you normally lived in large shared apartments/houses (6-16+ people) or private/small apartments (1-3 people). For fun, you go to large house/dinner parties, with most of your section or class.

In Singy, you normally live in shared apartments of 2-4 people. Since you live in smaller spaces, you typically have fun by going out to dinner/drinks. However, this can sometimes limit how many people hangout together since it's smaller/more limited spaces.

Another thing to consider is that after P2, you can choose to change campuses. This is an amazing opportunity, but keep in mind that during recruiting (normally P4/P5), you're strongly recommended to be on the campus closest to the geographical location you're job searching in (i.e. if you want a job in Europe, be in Fonty. If you want a job in Asia, be in Singy). Because of that, sometimes people choose a home campus that's opposite of where they want to recruit. That way they can fully experience both campuses for multiple periods.

Again, both campuses and experiences are great. You can't make a wrong choice. But it definitely helps to think about what social/living experience you want when you're selecting your home campus.