Freenet and I2P do have different sites, but I have never heard of any drug trade on either of them. Freenet is pretty much pedo central (even compared to Tor), not sure if there is anything worthwhile on I2P its really fucking small (it has like 5 thousand users). Tor is mostly used for surfing legal porn and getting out around firewalls, but it also has numerous other users. Tor has about half a million people using it at any given time, I doubt they are all drug dealers and pedophiles.