The I/O Usage limit differs due to the costs involved for the location and based on whether the server has SSD or HDD storage disks. For example, SSD is not available in the EU location because hardware costs are higher in the EU. If we installed SSD disks on the EU servers, we'd have to quote a different and higher price for them.
On the other hand, we offer more resources in some locations. Here is a list of services/features that varies depending on location unless mentioned otherwise:
5 MB/s in Los Angeles (USA), Chicago (USA) & Orlando (USA), 3 MB/s in Amsterdam (EU)