I agree with Wagy27.
I think if you want to get research done to improve your application, it's probably best to do it at your home institution given all the logistics involved.
Even if you want to do research at an institution to get noticed and develop relationships with attendings in order to match at a program, I would still favor doing a standard rotation. A typical rotation allows you to work with a number of attendings and gives you the chance to give the all important "talk" at the end of the rotation.
I've seen a couple of students kind of stuck in a corner for a month while doing research, so I'm not sure that their experiences were as useful as a typical rotation.
This isn't to say that a research rotation has no value--if my only option was a research rotation vs no exposure at one of my top programs, I would for sure do the research rotation.