What are some alternatives?
When comparing qBittorrent and rTorrent, you can also consider the following products
Transmission - Transmission has the features you expect in a BitTorrent client: encryption, a web-based interface...
Deluge - Deluge is a full-featured BitTorrent client for Linux, Unix and Windows.
BitTorrent - BitTorrent is a peer-to-peer program developed by Bram Cohen and BitTorrent, Inc.
Tixati - Tixati is a peer-to-peer file sharing program that uses the popular BitTorrent protocol.
Vuze - Vuze is a free BitTorrent client used to transfer files via the BitTorrent protocol.
WebTorrent Desktop - Stream torrents