With darker beers, obviously it's a little more difficult to tell the difference, but I found that a late extract addition lead to a lighter color in my lighter brews. I brewed two similar pale ales, and the latter used the late addition--it's color was more along the lines of what I was hoping for.
Another benefit of the late addition is less of the "twang" or burned marshmallow flavor. This improvement is noticeable in even darker beers.
I guess I'm assuming you're talking about DME/LME instead of AG...?