Hi Din,
The P2 and SxS media that you refer to are considered solid state media. This means when you shoot your video, instead of traditionally recording to tape, you're recording to a memory card. These cards are solid, which means they have no moving parts like tape, hard drives, and optical drives do. So there's potential for greater reliability in these devices as well as less potential for dropouts like you sometimes experience with tape.
There are countless differences in the recording formats that you mentioned. Feel free to ask specific questions on this forum.
For more information, the company that I work for has many FAQ pages and articles that you can reference. Here are a couple links:
P2 vs. SxS
http://www.tapeonline.com/faq/solid-state-memory-faq.aspx
More FAQs
http://www.tapeonline.com/faq/
Cale
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