I have a 13" MacBook Air, and the display is not large enough for me to feel comfortable editing photos on it. But then, I'm not convinced a 15" display would be enough, either. I have a 17" MacBook Pro (which I find acceptable for editing photos, although I do often connect it to a 27" Thunderbolt display), and I'm really hoping Apple brings the big boy back to the notebook lineup sometime soon! Regarding storage space, I was running low in space on the internal 500 GB HDD, so a couple of months ago, I swapped in a 960 GB SSD in the 17".
I suspect you're not getting any advice, because these are questions you can really only answer for yourself. How big a display do you need? How much onboard storage is sufficient for your needs? Both builds are more than sufficient from a computing power standpoint.