There is other reason why use snapdragon compare to tegra.

Because qualcomm provide 1 full solution for the device.
Asus just follow the design from qualcomm will do.
Do not need to find and match other ic.

Safe time and money.

But Qualcomm chip worst in stability and handling compare to samsung and tegra chip.
Hope nexus 7 have extra external codec that not from qualcomm (this cost from few $ to almost $20) or else, the sound quality will suck to the max..

Qualcomm chip is the worst statement is come from a team of software and firmware engineer who using Qualcomm package to build their product.