what is the difference between a San disk sd card and a regular sd card? Which one should I use in my p3 advanced? I just have a regular one in my p2 and video seems to be good.. Thanks

Use a class 10 card, higher write rate, better quality card. But no, theres no difference in card quality, memory is memory, its just its performance and speed thats different.

If you use an SD card that is not class 10 or better you will run the risk of the video locking up, dropping frames or simply not recording at all.

There is no visual quality difference from card to card.  It is a digital recording system.  It either works or it does not work.  There is no in-between.  If the card is fast enough to record the video stream it will work.  If the card can't keep up it will cause errors and the camera will lock up or fail to record.