The device is pretty similar to the Xperia Z1 and just has a few differences like intensely memory and some mine changes. But there is one more change which seems to be big and it does not even on the specs sheet. According to some of the sources, just like other Sony smartphones the device comes with a locked bootloader, but there is one more change and that is the bootloader cannot be unlocked while the bootloader on other devices can be unlocked.
Also sources say that denying the bootloader unlocking was actually done on a request made by the mobile carrier. So if you were hoping that you could flash a couple of ROMs on the device after buying it, may be you should go for the intensively Xperia Z1 version itself.