Urban is a bigger star, who has been in bigger movies...
Bigger movies? Saldana was the female lead in Avatar
, which is the highest-grossing motion picture in the history of the world, as well as the biggest-selling Blu-Ray release of all time. How is there a bigger movie than that?
Okay, Urban had a small role in Lord of the Rings
, but he was kind of buried under the huge ensemble. Other than that, the biggest movie he's had a major role in other than ST has been The Bourne Supremacy
As for which one is the bigger star, this is admittedly an imperfect survey, but "Zoe Saldana" gets 12.3 million Google hits while "Karl Urban" gets 5.6 million. Also, according to Rotten Tomatoes, since 2001 Saldana
has been in 32 films with a combined box office of $1.79 billion, while Urban
has been in 29 films with a combined box office of $1.58 billion.
So I just don't see what gives you the idea that Urban is a bigger star. Maybe he is in New Zealand, but not in the US or worldwide.
and McCoy still plays a bigger part. He's the current best friend of the main focus of JJ's movie...Kirk, and his story of growth to the 5 year mission. Uhura is secondary or even tertiary to this.
I'm sorry, did you watch the first movie? Uhura was made far more than tertiary, given close ties to both Kirk and Spock, even if her relationship with Kirk was adversarial. These films are clearly as much Spock's story as Kirk's, and Uhura plays a very important role to this Spock. And her role as gadfly to Kirk is comparable to McCoy's.