The laptop with i5 will be better overall. However, I have Autocad on my laptop as well as desktop, and what I like is a large LCD display when I work with Autocad. Consider this as part of your decision criteria.
Another important aspect is the speed. The computer (any) is faster than my designing speed in Autocad. The real designing is done in our brain, and then outputted to the computer. As a result, any computer running Autocad (or ProE) is fine with me.