Right now, I have a decently spec'ed 27" iMac 5k I bought a year ago and the new 13" Touchbar MBP. I'm a photographer and a teacher - so I do heavy LR editing but I also need a laptop to take from class to class on a daily basis. My thoughts are, however: why not get rid of both the 13" MBP and the iMac and go for a maxed out 15" TB MBP? I've always loved the bigger screen real-estate of the 15" model, but until now, it was just too heavy. I think I could probably live with the new 4 pound-version. I'd probably get an external screen for the 15" but I'm not sure I'd even need it. I know these are first-world problems - but what would you choose?