"The gateway to Austin"
I know Mopac Expressway have its detractors who complain about the constant construction or the stop-and-start traffic, but I think it's a great street, and I hate highways and expressways. Granted, traffic is sometimes bad, and granted, it seems there is often roadwork that is not needed, but Mopac will take you just about anywhere you need to go. i think of it sort of as the main artery to the heart of Austin. If I had to choose between this and I-35, I'd definitely take Mopac if your route allows it.