It is more apt to call Usenet different than better. The one major difference is most good Usenet services cost money while BitTorrent is free. BitTorrent is perhaps easier to get into for beginners, while Usenet is better for the tech-savvy and old-school computer users who know the best Usenet servers.
For file sharing Usenet is more direct and on average has better speed (depending on whether you are using the best Usenet provider). Nonetheless, the peer-to-peer sharing of Torrent content has become much faster in recent years thanks to the increase in uploading speeds of the average internet user.
Both can be used for legitimate file sharing and copyright infringement.