iPad mini if you can spare the extra few dollars. Really, go to a store and play with the Nexus 7 and Mini side by side for a few minutes and you'll see what I mean.
iPad feels infinitely better in the hand, and the display, while low-res, is really good. I've been looking for a reason to buy one, and almost considered even-trading my iPad 3 for it.
That said, I am a much bigger Google fan than I am Apple.
I owned both. iPad mini definitely has some nice points. It's so thin and light, feels extremely quality, unlike the Nexus 7 that was built by blind monkeys ASUS is using as slave labor. I also particularly like all the screen space. It's a 7.9 inch screen but physically that much bigger, the 4:3 ratio is awesome for webpages, and no gigantic on screen buttons wasting space (damn Google needs to fix that).
But my god, my eyes bleed looking at that 160 DPI resolution now. No matter how amazing everything else was, the screen resolution is just a deal breaker for me. I tried to like it and couldn't.
I'm hoping ASUS has the build quality issues mostly resolved by now. I went through 5 Nexus 7 tablets before I got one without the glass popping out the left side. Other than that though, I do love the feel of the soft touch back, and the narrow width makes it fit in one hand easily. The large onscreen buttons kinda suck and the color quality of the screen is not good, but it's sharp and I was able to forget about the washed out colors after a while.
I actually like the Kindle Fire HD the most. Though, I didn't mention it as a recommendation because you need to root it, load Google Play and some services, to make it a decent tablet, and that's not for everyone. I love that the colors are better, the speakers are amazing sounding for a tablet (and stereo in landscape), and the wifi is really nice. But it's also a slower tablet too.