mikeh,
I compared the TCE VP to the Digitech Vocalist VR and the Vocalist performer. I was most interested in the VR since it is a rack mounted unit and it was obtainable for around $350. I did not try out the Vocal 300 since it appeared to be more for live performance.
The big problem is that all of them are just so much fun to play with. Anyway, I selected to TCE because it was able to reproduce words "exactly" as spoken or sung. The Digitech units would produce a sound that was in pitch, but in most cases, it lost the quality of the words. If you are doing backgrounds where you simply want vocal Ohhs and Ahhs, or something close to the words, then the Digitech on a price performance basis is going to win.
For the applications I needed, (high quality demos and voice overs), I had to spend the extra cash to get the TCE.
As far as the effects, the Digitech and the TCE both have decent reverbs. I don't typically use the built-in reverb or compression in the TCE, unless I'm just fooling around and don't feel like moving a patch cord.
Of course, none of the processors can beat real live background singers who know what they are doing. But you don't have to feed them, they won't hit on your wife/girlfriend, they won't drink your beer, and they won't join a union. (Also a good argument for drum machines?)
Overall, on a scale of 1 to 10. The Vocalist VR would be around a five, the Performer would be a four, and the TCE would be around a seven. If I could find something at a nine or ten that was around the price of the TCE, I would definitely try to buy one.