Upgrading from a 2012 Macbook Air. If I go with a base model 2017 MacBook, how will the performance compare? Will it be faster due to be being 5 years newer, or will the lower-clocked processor mean that I'm actually downgrading from my MBA? Both would have 8GB RAM. Main reason I want to upgrade is the Retina display and sleek form factor. A secondary question is: is there any reason people have chosen the MB over the newest MBA, which I would also consider?