Beyond their improved power and speed, newer iterations of laptops also tend to be much smaller than their older counterparts. In many cases, you can even find models that are less than an inch thick.
When you are working with an advanced program like AutoCAD®, you need a top-of-the-line PC with the right specs. Those specs are for more than just pure power, though, because they also need to keep your designs safe from software crashes and interruptions.