with a 4.3 inch display, you will always be tied to how long your display is actually on for.
It isn't just Sony.
Now that said, some guys with the N/A One X are getting 30+hrs with 2/1-2 to 3hrs of display time. With tweaks they are getting 5-6 hrs display and 16hrs of battery.
Now HTC worked a lot with that battery to get the most out of it, AND they are running ICS.
When I run Juice Defender I can easily get 32 hrs out of moderate usage.
This is wo jd running.
Xperia S /4S / Xperia Arc / X10