I think it's difficult to judge from "The Cage" alone how Pike would have worked as a character in contrast to Kirk. Remember, at the beginning of "The Cage," Pike is coming off a major event in which several of his crewmembers were killed. He's naturally upset, and he's doubting his own ability to make good decisions. But that's not an indication that Pike is always a gloomy, brooding character. It is a reaction to a specific incident, which is what Boyce tries to make him see.
Then, for most of the rest of the episode, Pike is dealing with an extremely serious situation in which he is a prisoner and having his mind manipulated. Naturally, he's going to be rather serious during this situation.
But by the end of the episode, Pike's attitude has changed. When he banters with Boyce on the bridge at the end, he's rejuvenated and recharged and ready to move on to the next mission. Had we seen the character again, he might have been far more upbeat and outgoing than what we saw in "The Cage". One episode is simply not enough to judge by.