1) If you want to do anything graphic wise, you are going to want a dedicated video card and a strong CPU. So in your case the card pulls a lot of weight.
2) With programs like Photoshop and 3dSmax, the performance difference between 4mb and 2mb isn't very noticeable. (info taken from and X-bit review of the new Pentium Dual Cores).
3) Not sure I understand what you are asking.
4) Of the two, the Dell is better. Both are older models I think and you may be wiser looking at some of the newer models that have come out.
People don't like the Inspirons because they tend to come with a lot of bloatware. The Latitudes are business class laptops and are mostly bloatware free. The Latitudes tended to have better build quality than the Inspirons of old. Typically, Dell laptops are better than their desktops so Dell is a good choice here.