I manage two sites that provide the same service; even they use completely different texts, format, structure and even technology. I'll refer to them as oldsite.com and newsite.com.
The reason of keeping two 'duplicated' sites is because we remodelated oldsite.com completely to create newsite.com, with the goal to completely replace it as soon as it got a decent ranking.
Currently, newsite.com has a PR5 on toolbar, while oldsite.com has PR3. In Google directory both sites show PR4, but sorting by PR puts newsite.com higher. For oldsite.com, a link: search returns results 1-12 of about 15; while newsite.com shows 1-10 of about 13.
By examinating competition, I would expect that both sites have similar rankings (not top, but still good). Instead, oldsite.com ranks #8 and newsite.com ranks #349 for our main keyword.
Can somebody give any idea about what might be making a so big difference between the sites?