Reality competition shows celebrate the feats of singers, dancers, chefs, models and designers, making it next to impossible to single out one judge as the very best. Pitting one against another is like comparing Scotty McCreery and Hines Ward.

Most insiders agree that great reality show judges need expertise with what they’re evaluating, a distinctive-yet-authentic personality, and the ability to deliver honest criticism.

“You have to be unafraid, you have to take risks and you have to have the courage of your own conviction and call it as you see it. You have to be honest,” says “Dancing With the Stars” judge Bruno Tonioli. “You have to make a point that is obvious, giving a criticism that is clearly understood. They may or may not agree with you, but that engages the public.”

Nigel Barker, the longest-standing judge on “America’s Next Top Model,” occasionally receives hate mail from viewers who disagree with him, but shrugs it off. “The whole point of us as judges,” he says, “is that we’re telling contestants what they probably would never hear at an audition.”

Barker responds to authenticity in reality judges.

“If I don’t like someone as a judge, it’s mostly because I don’t believe them, or feel they’re camping it up or taking it to such an extreme that I don’t feel it’s actually them,” he says.

Outrageous as his co-judge Miss J can be, Barker says he’s exactly the same off camera as on.

Tonioli, one of reality TV’s more exuberant judges, admits that people who know him as a choreographer might not recognize the more jovial side of his personality.

“It is me, but it’s one side of me. I created this kind of character so I can give these heavy blows, but we can still laugh about it together,” Tonioli says. “You tap into part of your personality and expand it to make it entertaining, because if it’s not entertaining, people are going to turn it off and rightly so. If you’re onscreen, it’s part of your duty to entertain the public.”

The best judges can dish out honest, detailed critiques because they’re insiders first, judges second — “someone who has expertise and experience in the industry and can speak with authority,” says Padma Lakshmi, host of “Top Chef.”

Just as “Top Chef” judge Tom Colicchio is an actual chef, Tonioli has worked in dance since he was 18 and Barker is an established fashion photographer. Like other successful judges, they know whereof they speak.

“Randy Jackson (of ‘American Idol’) is a great judge. He’s very comfortable at what he’s doing,” Barker says. “He’s not trying too hard, and he’s enjoying the process. It isn’t ‘work’ — the whole thing is an experience, and it’s part of what he does and who he is. He’s spying talent all the time.”

Working well with fellow judges is vital, but as “Idol” fans know, creating and maintaining the right balance isn’t easy.

“Taking Paula (Abdul) out of ‘Idol’ didn’t work. It created a chill,” Tonioli says. “She and Simon (Cowell) worked well together and created an atmosphere that was very good.”

That said, Tonioli likes new “Idol” judges Jennifer Lopez and Steven Tyler, saying they fit because neither tried to be someone or something they’re not.

Whether shows are live or taped, reality judges must feel at ease on camera, which greatly decreases the pool of qualified judges. “There are a lot of very eminent people in our industry who just aren’t very communicative on TV,” Lakshmi notes.

As a Brit, Barker has noticed something a growing number of reality show judges such as Sharon Osbourne, Piers Morgan and Len Goodman share: English accents.

“Our voices and accents convey a certain element of authority regardless of whether we know what we’re talking about or not,” Barker says. “We get away with murder.”

King for a day | ‘Office’ table read | Judging reality show judges