AVCHD Full HD records at 24mbps. (3MB/s)

anything that writes sufficiently faster than that should be able to record in full HD.

actually, the sustained sequential write is more for photography & video. Class is only to show the minimum attained speed, but whether a card can sustain such speed over a period of time is what's important to prevent data loss & corruption. this is where the different brand of cards has different performance, thus the different pricing.

in otherwords, certain brand card are simply pricier becoz their sustained write speed outperform others, even tho having lower class rating. class rating is the least meaningful thing to consider if you are into burst mode & raw photo taking.

I am not misunderstanding yr words. i know what you wanted to say. And i stick to what i said, i dont buy according to class. i buy according to the actual write speed the card can perform. just because a card is rated class 6, it might not neccessary perform better than a "good" class 4 that has their sustained write speed performing above their class. e.g panasonic & sandisk class 4 SDHC.

google around for SDHC speed test done by others, and you will see certain cards perform very fast for sustain write even though they are sold as class 4, even better than certain class 6. class rating is not the best indication for performance.