Sorry, just thought I'd add a quick update. I ended up picking up the Rio over the Accent for a a few reasons; the dealership was willing to move a bit more on the Rio, Insurance was cheaper, and I liked the sedan a fair bit more. The only real downside I could see for the Rio compared to the Accent (for what I'm looking for) was a difference in the Lemon-Aid score for the 2006 models (same generation). The Accent was rated 5-star "Best Buy", while the Rio a 3-star "Average".
Not a huge concern by any means (I have a feeling it has more to do with KIA's history in North American than anything else), but what exactly does it mean when they say they "share the same platform?" From all my research and my test drives, it seemed like they were different styles of pretty much exactly the same car: same parts, engine, transmission, and even interior trim. Is that correct?