>Is the 6s and 7s use the same chipset?
Different chipset. Mediatek 6 for 52246S and Mediatek 7 for 52327S.
>Is the hardware of both drives are the same or totally redesigned?
Probably different, but there is no 100% conclusive proof on this yet.
>Which one has shorter casing?
>What's the writing strategy when RE-writting 24x and 32x of both drive?
>Why would LiteOn stop making 6s?
>What's the reason LiteOn release 7s after the 6s was made?
Manufacturing savings? Don't know, I'm just guessing.
>How is the error rate when bruning CD-r at 52x of both drive? Just rate
Not enough data available to compare.
>What function that the 7s is worse than 6s?
Not enough data to compare yet. Sorry.