- faster CPU (i5 2.5 vs 1.8 GHz)
- double the RAM (8 vs 4 GB)
- bigger HD (as you say)
- wider aspect ratio (Pixel has 100 extra pixels along the bottom in an overall smaller package)
- a bit higher (1.9 vs 1.6 cm)
- a bit heavier (1.62 vs 1.52 kg)
- bigger battery and runtime (74 vs 59Wh, reportedly 7 vs 5 hours)
Overall, a lot to be said for the rMBP. Good to have options.
- Thunderbolt
- USB 3.0
- Bluetooth 4.0
- Optical In/Out
- MagSafe
- Better Trackpad
Not to mention a company with a history of great support. There really isn't any good reason to buy a Pixel.
MagSafe is a big draw though, arguably as important as almost anything else. Comparing the screen on my MBA to the screen in the new Dell Developer laptop with IPS is a bummer though.
In all honesty, I've never even seen a USB3.0 device in the wild either. Not an argument against the option, of course.
edit: Actually, hotplug Thunderbolt is touchy in Linux 3.8 because Apple's thunderbolt implementation is back-ass-ward stupid, but that's not really a biggie, I don't use Thunderbolt for anything really (the display out is fine)