Dimensions etc. In autoCAD you can give command while drawing line for example, you select a line tool , click and start drawing line, you can give length in units like 20' and it will not draw more than 20'.
In sketchup i didnt find these kinda tools. AutoCAD is a professional software which civil, architects, car manufacturers etc use because of its accuracy. I find Sketchup to be fast but not that professional.. however thats my opinion maybe professionals also use it.