It's really striking seeing them next to each other like that.
iOS6 has class. It's unique, elegant, and yes, it might look familiar, something some people misinterpret as boring, but its a confident and classy look. It's timeless.
iOS7 on the other hand is loud, jarring and vulgar. It tries to go in all directions at the same time, using a gradient one way here, and differently there. But worst of all, it's bland. It looks like the result of trying too hard to hit all the checkmarks. It doesn't lead, it follows.
iOS6 has that timeless quality, that makes it look strikingly good the first time you see it, no matter what decade you're in.
iOS7 on the other hand, will look ridiculous and dated when the current trend of "flat UIs" has passed, in a few years.
Like the horrible unevenly aligned letters craze of the 90ies that claimed yahoo and eBays logos as victims.