Just answered a question at Urch about stating the reasons for choosing a specific school in an SoP and, more specifically, about stating that the reason is a specific faculty research . Thought my answer could be useful to someone later here.
I believe different people have different reasons to want a school. So, if your strongest reason is really a specific faculty I think you should go ahead and say it. And of course try to explain why in a convincing way. If that's not the reason, then you should tell them what is the reason.
I think too many applicants try to write what they think the school wants to hear, or try to follow a magic prescription for an SoP. Then the reasons sound weak, vague, generic, without personality. Because they are not the true reasons.
A combination of reasons can be important too, instead of just the strongest reason. Even if the faculty is your strongest reason, it is probably also the strongest reason in many other applications the school is evaluating.
Again, I didn't go too deep into that in my SoP (not enough space for that), but I was really asked about that kind of thing afterwards in the interview. And when I was asked, I was able to list reason after reason after reason. And many of my reasons wouldn't make sense for another applicant. Because they are MY reasons. It would be very hard to find another applicant saying the same things. By the way, I don't think my reasons were that amazing, but they were honest, and so I can be much more convincing that way.