Our old MB 13" is literally falling apart now and we need a new one. I see that the air is much lower then the MB. I know there is no disc drive so no adding DVD or other discs. What about external hard drives? I have one of those that I use for iTunes and whatever I would need to use it for. So what is the disadvantage for us to get an air? The main use would be for my wife who will be doing online college courses and me for iTunes. No disc drive is strange to me since every laptop I had always had one.