For me, TRS2004 is better. It's like comparing EMD to Baldwin. TRS2004 (EMD) works.
TRS2006 (Baldwin) appears, from the hour that I played with it, to be the same animal, only it takes up more disk space, more processor, and more time to get anywhere. In short, it's the gass-guzzling, lower horsepower, slower version of what I already had. It came with more content, but nothing that appealed to my modeling interests.
From the postings I've seen, there are a LOT of complaints about CMP, something I've personally not messed with. But Download Helper was no picnic, either. The biggest pain for me is that DLH seemed to stop working right about the time CMP/TRS2006 came out. Gee...
CMP and the ability to run TRS2006 content are the #1 and #2 reasons for getting TRS2006, according (once more) to what I've read. I have yet to find another reason to run it.
Adam