One reason (probably the main reason) to use Deluge, with its client-server stack, is you can run the server on a “seed box” which will allow you to manage your torrents on a server which is always up (and always seeding, when needed) from a client which is not always online (your laptop, for example). This is extremely useful if you are part of a private tracker community where users are required to seed the things that they leech.