Try this thread: http://forum.grailtone.com/viewtopic.php?f=24&t=47250
Personally I think the Tremoverb cleans sound better. (As well as every other sound on it.) I know a lot of people say the 3-channel Rectifier cleans are much better than the 2-channel, but I'm the other way round - I think the 3-channel cleans are sterile and harsh, even though they're 'cleaner' than the 2-channel. The Tremoverb is better for clean than the straight 2-channel too.
For what it's worth he's making the wrong comparison with Pushed vs. Blues, because Pushed uses the same channel and gain structure as Clean, which is different from all the modes on the Tremoverb. The Tremoverb's modes all use all the gain stages, so Clean and Blues are closer to Raw on the 3-channel. (The Tremoverb and 2-channel Rectifier are really *one* channel amps with complex switching, whereas Channel 1 on the 3-channels uses a different signal path.)