Some harddisks use a combination of vertical and horizontal mapping. As you can see in the above pictures, transfer rate is higher when data is read or written to the outer parts of a disk. The reason is that there is more space for sectors. The number of sectors varies in steps. That the reason why you see the steps in the transfer rates.
Some hard disk use the combination of 'vertical' and 'horizontal' mapping.
The 'horizontal' mapping is used in the zones, the 'vertical' mapping between the zones. However, transfer rate and seek time look the same to 'vertical' mapping. If you are going to buy a HD you have may need to know what kind of mapping the drive does. However, drives with horizontal mapping are not very common. You will find EIDE controllers integrated with the motherboard and that EIDE hard disks are much cheaper than SCSI drives.