It's been several years since my academic unit searched for a new faculty member. We're almost at the end of the application-gathering phase of a search right now, and I just spent an entertaining hour reading the files that have come in so far.
Faculty searches are very odd things. The existing faculty recommends who will join them. And existing faculty are not always interested in being shaken up. Administrators make the final decisions about who will be hired. And administrators are not always the best at distinguishing their runaway imagination from reality.
To read faculty search applications is to enter a succession of worlds in which the shape of the department, the opportunities for students, the courses taught, the collaborations possible, change with every new file you open. It's impossible not to visualize what life would be like with those courses and that research and that personality happening in the halls every day. And each one is different.
Depending on what potential future is most attractive to you, the faculty committee member, you can get really enamored of one of those files. Searches are like internet dating; you see your particular Mr. Perfect and get your hopes up. Then you argue with your friends about what characteristics in the profiles you all looked at are mostly likely to make for a good match. Finally, you meet up with a few of them and see how they measure up to your dreams.
Maybe the most interesting aspect of this process is thinking about the research interests of these candidates. If it's close to something you work on, you might be intrigued. But there's not much benefit to the department in having two people doing the same thing -- or having the ability to teach the same specialized courses. If it's not close to your interests, you probably don't care as much, and you can't judge as well whether that research will appeal to students or complement department course offerings.
In the end, it's not a scientific process; it's an attempt to judge whether relationships are worth building. That's always a matter of imagination, attraction, and probably unreasonable bias.