The Intel GMA4500 is an shared-memory laptop graphics solution. This means no dedicated memory for GPU to offload the graphics calculations into. Does it matter? Well, if you are going to either play rendered video games, watch hi-definition video disks, or use web- or desktop-publishing or image-editing software (such as Adobe After Effects, and others) the a "dedicated" graphics solution is a preferred choice.
That being said, there are more current solutions than the NVidia 9300. Basically, if your choice is just between these two machines, you will likely not see much graphics performance difference, because of factors other than just the dedcated graphics offload. Of the two, I'd go with the NVidia 9300-equipped device.
I do know that other Sony laptops come equipped with NVidia 200-series (210-230m) graphics, perhaps it's worth another pound of weight to get more graphics performance.
two final suggestions: write down your "wish list" CPU, RAM, Graphics, Disk, weight, price, screen size, warranty. Next, rank them based on your top "needs" versus wants. If graphics comes in 1, 2 or 3, then keep shopping past these current choices.
Athe other suggestion is to review the graphics comparison rankings at passmark (http://www.videocardbenchmark.net) . While these will hae desktop graphics benchmark performance numbers, some quick research will help determine the laptop device equivalents and you will then have a quantitatie source for graphics performance.
Hope any or all of this helps you!
(FYI, here's my current laptop spec: 5.6 pound Lenovo Y550P: Intel Core i720Qm CPU; 6Gb RAM; 500Gb DISK; NVidia 240m-1Gb VIDEO)
I do think the NVidia graphics will work better in the long run. Even better, the GeForce 230M featured in the CW series found here:
offers more video ram and a much faster graphics processing. Please take a look at it as an option....not sure if the color is right, but the speed/performance will work for photo/video/MatLab and more....think of it this way as well....you might end up owning it for a while, best to make it work for you.