Deluge is GPLv3 only. Qbittorrent is a mix of GPLv2 and GPLv3. Personally I'll stick to v3 since it includes specific terms that protect against modern DRM and ways to circumvent GPLv2.
Ah, right, I googled qbittorrent license earlier and accidentally instead read another similarly named project's license, which was MIT. You're right, Qbittorrent isn't really any more free than Deluge.