It is in your best interest to apply early to schools with rolling admission (although if you do PTCAS, those that don't do rolling admission won't look at your app until their deadline has past but those that do rolling admission will look at your app as soon as it is submitted). For example, Emory does rolling admission, and so they began reviewing apps as early as Sept (even though their deadline is technically in Feb). Same goes for Temple. When you apply on PTCAS, you submit your app to all of the schools listed. If, for example you submit in late Aug, those that do rolling admission will start looking at your app as soon as they can. Those that don't do rolling admission won't look at your app until after their deadline has past, so it doesn't hurt to apply early to any school.
The notion that applicants with bad stats should apply early depends on what your stats are, I feel. That is because if you apply early, you are competing against fewer applicants, which will increase your chances, but if your stats are not good enough to even meet the minimum requirements of the school, then the school will likely still reject you. So there is still that chance you might not get accepted even if you apply early, but it does significantly increase your chances.
