I've seen several mentions of combining these ( Melo + Waves or Melo +AT)
Melo for the heavy lifting tuning, and Waves or Auto Tune for the overt character that they tend to impart.
There may be something to that for pop hit type songs.
As an aside, on quickie projects I've thrown Waves Real Time over the track and just spot tuned sections that it doesn't get right in Melodyne. It's a very down and dirty way to tune it quickly. 10-15 min you've got a very passable track. For anything real, Melodyne alone should get you there with optimal results.