@Osikiri I have requested more info on why there is such a difference between the above mentioned devices.
I also have a good piece of information on why there should be a difference between the two architecture types (32bit vs 64 bit) and given as examples a Z3 and an X compact.
When you compare two different Xperia™ devices running the same Android™ version, you might notice that the Android™ system file size differs. For example, the Android™ system in the Xperia™ Z3 uses 4.43 GB while the Xperia™ X Compact uses 10.22 GB, even though both devices are running Android™ 6.0.1. There are several reasons for this difference in file size. One reason is the amount of memory reserved for future updates, and another reason is differences in the actual system size.
The Android™ operating system is always stored in a separate, locked system section of the built-in memory. The size of this overall memory section cannot be changed after production. That is why Sony Mobile always reserves a sufficient amount of memory section space to allow for new Android™ versions to grow. This in turn means that a device that has just been released to the public, such as Xperia™ X Compact, has a considerable amount of empty system section space, while an older device such as Xperia™ Z3 has filled up most of that system section space during consecutive updates. Since the size of future Android™ system updates isn’t known beforehand, there is a margin to the reserved memory section space, to make sure that memory limitations don’t stop a future upgrade.
The Xperia™ Z3 is a 32-bit device, while the Xperia™ X Compact is a 64-bit device. Due to how the Android™ system is designed, the program code for the same application will use up more memory section space in a 64-bit device than it does in a 32-bit device. Exactly how much more depends; some parts of an application, such as images and sounds, will take up roughly the same space, but in general, the application may be 50% larger or more when installed. The same applies to an even higher degree to the operating system, since the system is mostly made up of code and very little graphics and sounds. The end result is that a 64-bit device will use up more of the available memory section space to store the Android™ system and any applications. This is not a Sony-specific condition but applies to all Android™ devices.
alexdon
