Don't conflate torrents over Tor with torrents over i2p. If you torrent over Tor, you will not only harm the network (not just from the actual torrent traffic either; building all those circuits is a toll in itself if you'll remember that botnet that used Tor for CnC a few years back and just sat there and made a bunch of circuits), you'll also gain no anonymity because
a) most clients will send your clearnet IP since they added in proxy support thinking of censorship and not surveillance,
b) Tor doesn't do UDP, and
c) the torrent protocol has a very unique traffic fingerprint.
On i2p, modern clients have considered a, b doesn't even apply, and i2p intrinsically protects against c. Tor is made for the Web. i2p is made for everything.