Personally, I didn't find the extra screensize of the 7730 worth the increase in form factor, the backlight is noticeably better, but it obviously harms battery life and you also end up using it a lot more since its presence makes the screen quite a bit darker than that of the 7230.
One other disadvantage that may not be an issue to you is the non-standard connector of the 7730, the 7230 uses a standard usb cable that also works fine on my camera and mp3 player so thats 2 less cables i need to carry around.