Well, is the GT330M more expensive, and if so, do you need it? It's decent for gaming with low-medium quality settings on modern games, you can probably max out older ones. If you just need a half decent graphic card for w/e, very light gaming or anything, just go with the Mobility HD 5470 if it's cheaper. Memory size won't matter, no doubt the resolution is too low to make any use of it.
If you can't decide, then get the Sony if you like Sony, Dell if you like Dell.