I was only being half ironical in my reply.
You have to realise that with the possible exception of InstantCopy, these transcoders compress. Some make a choice of how much to compress, and where. Some even allow you make that choice. But compress is ultimately all they do. Their ability to influence quality by their own excellence is limited - and ultra dependent on the quality of the original MPEG encoders used by the studios, which are not, I might add, of uniform quality. In practice, you wouldn't want your life to depend on being able to distinguish the output of trancoder 'A' from transcoder 'B'.
And yet, and yet.. People will declare to you how brilliant one is and how lousy the other is. This is usually based on an examination of still frames from movies - an uncertain principle in any case. I've even seen comparisons drawn where the frames where actually different! It's ludicrous.
In the end only you can tell. Your playback equipment, the quality of your screen, its size and, yes, the acuity of your vision, and God knows what else, all come together in a unique combination. It matters not if we amass an array of bitrate analyzers, 'scopes, fast Fourier transformations and all the rest if you don't like it. They're your copies/backups and they only have to please you, no one else.
So try them all and try to reach your own conclusions. There are no shortcuts.
There, is that better? Does that help:)
Onion replied while I was writing this reply. As you can see, he says much the same thing, only he is much more polite...