The reason why the advice on this topic is so variable is because the combinations of "your competitiveness" + "program competitiveness" + "your personality" are numerous.
For example, if you are indeed competitive for the top programs in Cali (Stanford, UCSF, UCLA), you will not need to do an away at a less competitive program (UCI, USC, Harbor) to get into those programs. Your stellar application will undoubtedly score you an interview and hopefully you don't mess up your actual interview.
That being said, most everyone that matches at Stanford/UCSF will also have very competitive applications. Unless you scored a 270 to really set yourself apart, they'll probably view a 242 and a 252 similarly (eg. Wow this guy killed it). So this is where "your personality" comes into play. If you know how to play the social game, shmooze with the PD during your away without looking like you're just kissing a**, it would behoove you to do an away at these competitive programs. I would just imagine that when the committe is ranking applicants, if they come across 2 nice interviewees but 1 one was also an away rotator, their perception of the rotator actually being a nice guy and pleasant to work with would be all the more strong.
Another situation that this can help in is if you are somewhat competitive and your personality can push you over the edge positively. How can you gauge if you will do well on an away? My advice is to look at your 3rd year clerkship CLINICAL (non-Shelf) grades and the comments. If you are consistently killing these areas, I think you can be pretty sure you'd do well on an away.
Hope this helps. This was mostly based on my own experience.
