The sweetfx screen just looks a bit darker to me. What more does it do? My main problem using the 3D option is getting sharp detail in the distance and some annoying flickering in highlights and reflections.
You can do things like de-saturate or over-saturate the colors, remove some of the colors, change the gamma, separately adjust tint for shadows/mid-tones/highlights, all sorts of things. In my settings, I've de-saturated a little, removed some of the red to make it look less "glowing orange everywhere", biased the colors more towards blue in the shadow and mid-tones, and also removed some of the haze effect to make it look more like "outer space".
