Things to consider:
I've been repairing Apple laptops for many years and there are some things you should know about them:
The current unibody design (pre-Retina Display) uses hard drives that can be upgraded, has an optical drive, has most of the common connectors built in, has RAM that can be upgraded and has a battery which is structurally distinct from the frame. All of these are advantages from a repair and reliability perspective that the Retina lacks.
All Apple laptops are extremely delicate in the following manners:
They are very very vulnerable to liquid intrusion through the keyboards and ports.
The wireless antenna is built into the screen hinge, making it vulnerable to liquid intrusions.
The glass face/zero clearance LCD panel is extremely vulnerable to closing foreign objects between the keyboard and the display, resulting in long shards of glass being created by the break.
Apple laptops are almost frictionless in the hand and are shaped like bars of used soap so it's very very easy to drop them while lifting them from or into laptop bags or when holding them in a vertical orientation while closed. (This also contributes greatly to their falling from tables by scooting off like hockey pucks)
Apple will NOT cover accidental damage of any kind and will void any warranty you may have if they determine that anything like the above has occurred.
Apple's regular limited warranty covers ONE YEAR from the point of purchase and requires registration for activation.
Buying an AppleCare plan is ESSENTIAL as it triples the warranty duration and makes you eligible for all the inevitable recalls, reworked parts and other "known issue" coverage Apple is obliged to provide undr California law for a total of SEVEN years.
With all this in mind I'd say that if you insist on buying a new Apple laptop, which for the first time in my life I can say I no longer want to support, I'd either do a maxed out Retina as it will have the longest lifespan based on it's stats being high enough to meet OS standards for a very long time or the 15" non-retina as the screen is still large enough to do serious graphics work on.
Keep in mind though that if you get the Retina MBP you will only have Thunderbolt and USB3. Thunderbolt breakout adapters are hard to find and really expensive. You'll need one for Ethernet, Firewire 800, DVI, VGA and pretty much everything else that isn't Thunderbolt, Displayport or USB3.
Personally I'd look into the high end notebooks built by Asus and then put Linux Pear or Linux Ultimate Mint Edition on it as the OS is both free and in many ways better than both Mac OS and Windows.
The 13" and the Air are like clutch purses... cute, convenient and utterly useless for anything more than ID and lipgloss.