Why do you need a Nexus 7 anyways?
With your 4.7in+, 720p/1080p android smartphone, why are you buying a Nexus 7 tablet? It's 2 inches larger, with a similar pixel density, a larger screen, and can't make calls/texts. It'll also have the same storage space as your phone, and same apps. So why buy one?
On the iOS side, the iPhone is much smaller (3.5/4 inches) so a larger consumption device (8inch/10inch iPad) has an identifiable niche. And of course, the iPad has apps "tailored" for tablets.
On the windows side, Windows 8 tablets offer productivity, and in the case of full windows 8 - a full on computer operating system. They also have usb ports, and all that jazz. The app store is also slowly budding. It's also something of a new experience since RT/8 are different from WP8, especially since each has their own marketplace.
So what's your rational, not that you really need one - at that price, it's easily in "impulse buy" territory as far as gadgets go.
Edit: I guess 200$ for a larger viewing experience sums everything up. Right now I’m on an android phone (HTC One S) but if I ever switch to iOS or windows, this tablet will be very compelling. For now, it’s tantalizing at 200$, but not worth it still.