Here are where I see the use cases for the different sizes of MB Pros: 13": you do work on the laptop, but you also do a fair amount of travelling. In this par

Here are where I see the use cases for the different sizes of MB Pros: 13": you do work on the laptop, but you also do a fair amount of travelling. In this particular case, the MB Air is also quite good. 15": you do quite a bit of work on the laptop, including connecting it to an external monitor, but would still like the laptop screen as a second monitor. This is definitely the best all around option, especially if you do some travelling/commuting but not all the time. 17": you need the extra screen real estate for something like video editing/graphics editing while on the move. Other than that, it's a bit bigger and heavier than most people find comfortable.