While I agree with Cher that The Voice is WAY better than Idol and that Idol could be mean at times (especially with Simon in the judges panel), I don't know how much we can actually praise The Voice and its judges for being "nice(r)" or "more positive." After all, the show is basically by invitation only, so the judges don't have to sit through bad performers to begin with. It can't be too much of a feat to be "nice" under those circumstances.
But still, The Voice >>>>>>>>>>>>>>>>>>>>>>>>>>> Idol (and I'm sure also The X Factor's U.S. version).
Idol is too heavily influenced by the tween girl demographic. The producers care more about being able to say "WE GOT 5,000,000,000,000,000,000,000,000 VOTES LAST NIGHT!" than they do about actually finding someone with legitimate talent and staying power.