ElDiablo summarized it up.
Plus then the hard drive size.. and the RAM size.
I got myself the simpler one a few months ago, with 256 MB graphics card. I do mostly virtualization, photography etc etc so moderate use (but with bigger hard drive, and external hard drives etc). As I shed the cash out of my pockets, I got the plainer one - either I will use a desktop for more graphic/stressing work, or if I will be doing work where the difference between 256 or 512 MB video card matters, then the contract or the employer better get me the other one

I don't regret.