My take is not "unique." I think you will find that many Okinawan karateka feel the same way. As for specific differences, origins, etc. as was asked about earlier, the Pinan were created by Ankoh Itosu when he used the kata Kosokun (Kushanku) and a now lost kata called "Channan" to develop them. The Pinan did not exist in China, although many Okinawan kata did develop from Chinese influences. So, the Pinan are unique Okinawan kata. Funakoshi took them to Japan and what later became Shotokan called them Heian and switched the order of Pinan Shodan and Nidan because he felt that Nidan was easier to learn. Shotokan actually does them a bit differently from Shorin ryu or Shito ryu, but they are recognizably the same kata. Shotokan introduced their back stance and placed a deal more emphasis on the straight ahead, linear, one strong powerful punch philosophy. Shotokan uses very few neko ashi dachi (cat stance) and very few sanchin stances. The Okinawan versions are full of these stances, which changes the flow and intent of the kata. So, even though Shotokan is doing what are recognizably Pinan kata, they are different.
As to Korean versions: I hear TKD and TSD students talk a lot about fluidity, but I think they must mean that they can do the kata fast and without having to count. There is a bit more to it than that. There are no high kicks in the Okinawan Pinan kata...period. There are no side kicks in the Okinawan versions, either, especially not head high side kicks. I have seen versions of Pinan with crescent kicks in Pinan Sandan, but mostly that is Shotokan. As for "inside out" crescent kicks, that is silly. Okinawans punch differently, they breathe differently (many TKD and TSD students hold their breath), and they have a completely different view of how one develops power and when it is used. These are things that a senior in Okinawan karateka can spot immediately. Most of us know very well the differences between the Shotokan versions and the Shorin versions and the Shito ryu versions. We appreciate the differences and understand the historical rerasons for them...but, the philosophy of the kata is the same (especially among the Okinawan ryu).