WD model help

[Tosk]

hi can any 1 tell me that the difference is between these models please

500 GB Western Digital WD5000AAKS
500 GB Western Digital WD5000AACS
500 GB Western Digital WD5001ABYS

and witch 1 is best?

thanks for any help

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and would you go for

2x Western Digital 500gb drives or 2x Samsung 500gb HD502IJ Spinpoint F1 ?