This could be phrased into a more broad question about how bit torrent handles clients trying to get a torrent, but my particular case is a bit special:

I have downloaded "TorrentA", which is a somewhat rare file with a ratio of less than 1, usually 0. Chances are that no one will ask for it for a long time.

On the other hand, I have "TorrentB", which is a widely popular file with a ratio that gets quickly above 1 and usually people leeching it.

Now, my question: If someone wants to get "TorrentA" but "TorrentB" is keeping my client busy, will the system/client (Using deluge) prioritize the less shared/known stuff, or is working on a first-come-first-served basis?

I'm asking because honestly, I would rather share the "popular" torrent to a ratio of 1-2 and then stop it to allow people get the weird stuff (If there's someone), but if the system will take that into consideration, I can just leave everything be and only delete files basing in storage space.