Disappointed with Retina Macbook 13 need a compromise

[awesome12]

i need to replace my x series lenovo badly and have been eyeing a mac for quite some time. like many of you, i was disappointed with the retina 13's offerings but i cannot wait for haswell.

so i'm up between the macbook air 13 and the macbook retina 15. i heavily multitask and do a lot of web dev, photoshop, youtube, and other media consumption like streaming movies/live sports etc.

the retina is intriguing because of the extra screen estate. i was planning on using quickres or similar applications to unlock more screen real estate for the retina display. this is a plus imo but i understand there is a performance hit when forcing the rmbp to display unsupported resolutions

though portability is a factor (i'm coming from a 12 inch ultraportable) i find that i hardly walk around with my laptop compared when i was a student walking around campus because i now go from car -> coffee shop or car -> library. is the footprint for the 15 rmbp too much? (like for instance if i were to travel by plane would it fit on the tray?)

i don't expect to game on the laptop so the discrete gpu may be a waste but are there other benefits of having a discrete gpu other than driving the retina display?

what irks me is seeing battery benchmarks of the retina 15 (when forced to integrated) matching or even surpassing the macbook air 13.

what draws me to the macbook air 13 is the footprint and possibly thinking that the processor and ram would be sufficient for my needs. i have a desktop at home so this would not be my main computer but i'd like to be mobile as much as possible and not have to rely on my main computer for work.

help?

TL;DR i want a macbook with 13 inch size but with the internals of the 15