Today I was looking over my HDD datasheet(a Western Digital 500GB WD5000BPKT) and I noticed that for its entire family, the "Performance" row "Host to/from drive (sustained)" is nominally decreasing in read and writing performance due to a capacity decrease:
This makes me wonder why. I didn't notice any other parameter that differs on this table except for the device capacity (750GB to 160GB). I also looked for other families and I found the same behavior (Samsung and Seagate don't show this performance parameters on their datasheets).
So, considering that all disks belong to the same family and are in essence the same, does someone know the exact physical reason for this behavior?