I used V-vocal for a long time, even tho I had a version of melodyne. the version of melodyne I had was not a vst, it had to be used stand alone (or rewire, but that never worked well). so I prefered to use v-vocal since it was so much more convenient.
but since I "upgraded" to the new version of melodyne and I can use it as a vst, I use it exclusively now. I had more "artifact" issues with v-vocal than I do with melodyne.