The 5V/1A socket is specifically for cell phones or electronic devices with the same capacity.
The 5V/2.5A is specifically for tablets.

Most electronic devices charge more quickly using the 5V/2.5A socket.
But please note: we recommend that you avoid doing this as some products may not be fitted with a protection device and may absorb this current overload.
This may result in damage to your electronic device.

If in doubt, always use the 5V/1A USB port.