Probably on raw computing power, not considering the video part Guest. Also consider they talk about the counterparts meaning dual core Atoms (Which some probably come with Ion). Though price-wise they can't be beat together.
Indeed, benchmarks show Zacate to wipe the floor with Atom, except for heavily multithreaded tasks, where it catches up. The Zacate laptops stand firmly above Atoms, but bellow Core i3, at an Atom-like pricing. While still trashing Intel's integrated GPUs.
As an Acer Aspire 5253-bz602 (Amd Fusion E-350) laptop owner and user, I play Counterstrike Source at 45fps with details high, medium texture, HDR on, and 4X MSAA enabled at 1366x768. After heavy gaming, the laptop barely registered as being warm. All at $329. Contrast to my old Aspire core2duo with nvidia 8600mgt, which ran hot as hell.
The AMD E-350 fusion runs about as fast as my desktop, Pentium D 820 (2.8mhz). I know of NO atom reaching parity yet with my CPU/CPU combo.
Correction: In an earlier version of this post it was wrongfully stated that the Fusion CPUs tend to underperform against Intel's Atom. The opposite is usually the case as covered in our early look to the AMD Zacate/Fusion processor last February. See the full review here: https://www.techspot.com/review/364-amd-fusion-asus-e35m1-m-pro/