I got the Macbook Pro Retina and I'm not sure if it was worth the extra dollars and the very small amount of extra weight. I think I would be fine with an Air. In fact, if I did it over, I'd get the Air and then spend a little bit more along with the difference in price to create a nicer desktop machine.
For me, it was between the Zenbook and the Macbook Air.
To be honest, the first thing I would do on a Zenbook is put Linux on it (I just can't develop in Windows any more, I don't know if something is wrong with me, but everything just feels wrong when I try). I reasoned this way:
1. If I ever decide to do iOS, the Macbook is a plus
2. It's UNIX-compatible, and pretty much a hop, skip and some GNU tools from linux.
3. If you really want to, there's pretty well tested software for putting windows on it.
Then I went on craigslist and bought a $500 Macbook Air (10"), and have been happy with my decision ever since.
I should also note that I do most of my programming on my desktop.
As another option, the Thinkpad T440s just launched. It has an option for a 1080p IPS, weighs about 3.5 lbs, and has a hot-swappable battery.
Lenovo also has really good Linux support.
Judging from your other comment, you have already picked OSX. If it works better for you thats all that matters, but its silly to pretend that you can't comprehend why other OSs exist. The answer is simple, not everyone likes the same thing.
Unfortunately, I didn't have enough for a rMBP, so I ended up spending a third of the cost of a 13" rMBP on a Thinkpad so I could run a dedicated Linux machine.
That being said, if someone just happens to prefer Linux, you really can't beat a Thinkpad from the T, X or W series'.
If you like OSX better than Linux or Windows, it makes more sense to get a Macbook. If not, Lenovo has a better screen at a lower price than the rMBP, and at the same price as the MBA.
The next gen of it is the ASUS Zenbook UX301 [1] with the insane resolution of 2,560 x 1,440 on a 13" IPS touchscreen. It's bundled with Windows, but Linux runs very well on them. Mine has been running linux since last christmas. Price is equivalent to the MBA.
[1] http://www.engadget.com/2013/09/04/asus-zenbook-ux301-hands-...
Second choice would probably be Lenovo's newer generation IdeaPad, then again it's really about what you're personally looking for and what setting you'll be using it in.
Unless you're going to be working in Windows, since Windows doesn't play so well at higher resolutions.
For example, the Macbook Air has excellent build quality, a great keyboard, decent (but not stellar) color reproduction, and an operating system that is well supported by pretty much any tool that a web developer or designer would ever need.
There are plenty of ugly tools that are capable of making pretty much every artificial thing on the planet that's considered beautiful.