I'm the developer behind littr.me. In my mind, the best reasons for migrating to your own service as a reddit community is the fact that you get ownership of it. You can monetize, you can enforce rules that are different to reddit's, you can focus your interface more specifically towards custom UI, etc.
The main downside of moving off reddit would be that you lose access to the larger pool of reddit users and communities. That however is mitigated by the fact that federated communities can still interact with each other despite being independent services.
Personally this would be my main goal for the project: managing to get one of the cool subreddits to leave reddit in favour of starting their own independent community using my code. However some of the things that are made easier by the centralized model of reddit are quite more difficult in the federated case (moderation as an example), and I don't feel confident (yet) to push for this.
The main downside of moving off reddit would be that you lose access to the larger pool of reddit users and communities. That however is mitigated by the fact that federated communities can still interact with each other despite being independent services.
Personally this would be my main goal for the project: managing to get one of the cool subreddits to leave reddit in favour of starting their own independent community using my code. However some of the things that are made easier by the centralized model of reddit are quite more difficult in the federated case (moderation as an example), and I don't feel confident (yet) to push for this.