The screen upgrade is obvious of course.
Is the rMBP more future proof? Can stuff like RAM, SSD be upgraded or all they all soldered on to the motherboard just like the Air?
the rMPB is the better machineas far as components and screen, but the air is more portable and the battery life is as long as a marathon of all 3 LotR directors cuts. purchase according to your needs.
What are some areas the 13" rMBP will truly shine over the 13" Air?
The graphical performance is almost the same since the HD 5000 and HD 5100 GPUs are identical (5000 is for the 15W processors while the 5100 is available in the 28W processors).
Same as the Air, all soldered on.