What are some alternatives?
When comparing eMule and BitTorrent, you can also consider the following products
Soulseek - Soulseek® is a unique ad-free, spyware free, and just plain free file sharing application.
qBittorrent - Lightweight and open source torrent client that runs on all major platforms.
Shareaza - Shareaza is the most luxurious and sophisticated file sharing system you'll find.
Transmission - Transmission has the features you expect in a BitTorrent client: encryption, a web-based interface...
aMule - aMule - the all-platform P2P client!
Deluge - Deluge is a full-featured BitTorrent client for Linux, Unix and Windows.