I don't know anything about Perrin or Opella. However, I know that Ternansky is probably the best Ochem teacher in the school. The material on his tests is difficult, definitely intimidating. However, you may gain the most intellectually by taking his class.
I took OConnor for 140A and I personally liked him. The material he tested on was very fair and relevant. He's also quite funny. That being said, his lectures aren't completely organized. He is extremely knowledgeable about the subject so he pretty much wings it, which worked for the most part.