Finally of course, there is the FUD factor - file sharing software in the Windows world is a NOTORIOUS source of viruses, worms etc. I am not dipping my toes in that water unless I really need to.
Just to bring up an issue that has not been mentioned previously, but seems to be of concern here. There have been numerous instances of vulnerabilities in RSYNC. It has been troublesome in the past and probably continues to be an issue. I was first enlightened and made aware of that when a bank of servers was compromised through RSYNC. I was not involved in the cleanup, but I am certain that RSYNC was the way in. I have used RCP and RSYNC in the past and have put them aside since it is rather slow and tedious and really did not impress me. It was used primarily to back up or sync files between servers then and I believe that is one of the primary uses for it today. I'm sure that you can run a Google and find out more about how it works and how to work it. I'm certainly no expert on using RSYNC, so I will not attempt to give you any help there, since it appears that issue has been addressed here before. It might be interesting to play with, but I would avoid it for serious downloads of significant size. I use FTP and BitTorrent with great success. I am not aware of any instances where a system was compromised by the BitTorrent software or directly by it's use. I will make that statement only for the Official BitTorrent and not for any of the similar programs that might be available. It is usually the downloaded content that would put someone at risk, just like the pirated content of the P2P file sharing programs that once were so popular at one time. The software packages themselves were often loaded with malicious garbage. They made me loads of money just cleaning up infested systems for people that know better now. Before you get serious about RSYNC check out any security vulnerabilities if that is a concern of yours.

I will strongly agree with Harry Kuhman to the extent that BitTorrent is a good choice. In my experience, it has not yet failed to deliver a valid and correct file. I hate to download something twice, especially something of DVD size. I have the DVD Torrent seeding from two locations intermittently. It has little impact on my regular use of my connections, and they are about half of the 6Mbps connection that you have. The BitTorrent program downloaded the files for me in about 4 or 5 hours the FIRST time I tried it. It was in the very beginning of the Torrent and Seeders were outnumbered by leechers at least 8 to 1. Most others that try Bit Torrent have good results. I use FTP quite often also, but have had rather inconsistent results with these large files, although I have not experienced the failures that you have. Mine just goes slow on a slow server and can end up taking more time than I would expect.

Other than that, let us know how you make out with it. It would be interesting just to make a comparison in download methods.