I use a mid 2012 retina MacBook pro i7 with ssd. Buying a second mac, intending to leave the 2012 at work. I was leaning toward the 5k iMac, but then, because the rMBP has been so great (even as a "desktop" with my ext keyboard and monitor), I wondered if there might be some added utility in getting a second MacBook pro instead of the iMac. Is there a precedent for owning two macbooks? Any preferences to this over the desktop model? Thank you.