Runs games on high settings, 1920x1080, HD video editing, very limited photo editing, and just basic functions like Office and Firefox.
If you aren't getting to the limits with the 4GB you have, I'd go for the 4GB config. If you decide later you need to speed things up, add the RAM yourself, probably cheaper than the bump in specs the laptop maker would charge. I think intensive 3D CAD might use a lot of RAM, or if you're running your HD video program with a game or two going, with a few browser windows open, etc. It's probably more about the number of programs running. You could try opening a bunch of things and check your resources in Task Manager.