First of all, Phil Schiller doesn't even know what he's talking about. He said the bezel of the nexus 7 is plastic. Its not. Its aluminum. He flat out lied on stage. Second of all, it has a better screen than the iPad, better cpu, twice the ram, and gps in all models. Its also a nexus device which means instant OS upgrades. The nexus series actually has a better track record for upgrades than even apple. The original xoom (it sold alongside the ipad 1) and the nexus s have full blown jellybean with google now and every feature, not stripped down versions like the iphone 4 and ipad 2 have. The back of the nexus 7 is a soft touch leatherette material and just about every review has praised the feel of it. Many actually prefer it over hard aluminum.
The screen is arguably the most important attribute of a tablet, and the Nexus 7's is mediocre (viewing angles, washed out, colors way off after viewing videos). I haven't seen the iPad mini in person, but I expect its screen quality to be superior to the Nexus 7. Yes the Nexus' 1280x800 is nice, but I'd be OK with losing 23% of the pixels while gaining both quality and size (the iPad mini's screen area is 36% larger).
The Nexus 7 reportedly has widespread quality control problems, and my own anecdotal experience supports this. I had to swap out two of them before finally getting one that wasn't defective (and it still has a minor blotch in the middle of the screen under the glass that I decided to live with).
Fit and finish is poor: All three of my Nexus 7s had the left-side screen rise/flex (though the third one isn't as bad as the first two). The iPad mini is more expensive, but if build quality is anything like the larger iPad, it's going to blow away the Nexus 7.
I'm not sure what the clock speed of the iPad mini is, but I'd be surprised if its A5 isn't at least as zippy as the Nexus 7's Tegra3.
Another advantage to the iPad mini is that it's thinner and weighs less.
Having written that, I prefer the Nexus 7's 16:10 aspect ratio because it allows for a narrower device. I haven't held an iPad mini, but being 5.3" wide will make it less portable and more of a PITA to use one-handed. For me, that form factor difference combined with the price advantage offset many of the iPad mini's other advantages.